Transforming a Valve Metal Layer Into a Template Comprising a Plurality of Spaced (Nano)channels and Forming Spaced Structures Therein

ABSTRACT

At least one embodiment relates to a method for transforming at least part of a valve metal layer into a template that includes a plurality of spaced channels aligned longitudinally along a first direction. The method includes a first anodization step that includes anodizing the valve metal layer in a thickness direction to form a porous layer that includes a plurality of channels. Each channel has channel walls and a channel bottom. The channel bottom is coated with a first insulating metal oxide barrier layer as a result of the first anodization step. The method also includes a protective treatment. Further, the method includes a second anodization step after the protective treatment. The second anodization step substantially removes the first insulating metal oxide barrier layer, induces anodization, and creates a second insulating metal oxide barrier layer. In addition, the method includes an etching step.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a national stage entry of PCT/EP2018/068683filed Jul. 10, 2018, which claims priority to EP 17181782.8 filed onJul. 18, 2017, the contents of each of which are hereby incorporated byreference.

FIELD

The present disclosure relates to methods for transforming a metal layerinto a template comprising a plurality of spaced channels, e.g.nanochannels, and to templates obtainable by such methods. The presentdisclosure relates to methods for forming a plurality of spacedstructures, e.g. nanostructures, inside the plurality of spaced(nano)channels of such a template, and to devices comprising suchplurality of spaced (nano)structures.

BACKGROUND

Solid-state batteries, and more in particular thin film solid-statebatteries are attractive energy storage devices. Solid-state batteriesare based on solid-state battery cells typically comprising a stack of afirst current collector layer, a first electrode layer (e.g. a positiveactive material layer or cathode layer), a solid electrolyte layer, asecond electrode layer (e.g. a negative active material layer or anodelayer), and a second current collector layer. The batteries may furtherbe encapsulated, such as for example in a polymer package.

In the example of solid-state Li ion insertion battery cells, thecurrent collector layers may comprise a metal foil, such as a foil ofaluminum, nickel, or copper and the active cathode layer may for examplecomprise lithiated transition metal oxides or salts, such as lithiummanganese oxide (LMO), lithium cobalt oxide (LCO), or lithium ironphosphate (LPO). The anode layer may for example comprise carbon,silicon, spinel lithium titanium oxide (LTO), or metallic lithium. Thesolid-state electrolyte may comprise glassy, ceramic, crystalline, orpolymer lithium-containing materials. Due to the high electric and ionicresistivity of the active materials, the anode and cathode layerthicknesses are limited to less than 5 micrometers. This results in alimited energy and power density of the thin film solid-state batterycells.

To overcome these limitations, three-dimensional electrode structuringhas been proposed to increase the surface area of the electrodes, thusincreasing the amount of the active materials present in a unit area ofa battery cell. In such three-dimensional approach, one of the mainmanufacturing challenges is conformal coating of battery materials onthe three-dimensional electrode surfaces. Another challenge is the usefor advanced, possibly low-cost, methods for manufacturing thethree-dimensional electrode structures.

A three-dimensional electrode structure may for example comprise orconsist of a plurality of electrically conductive nanowires orientedalong a same direction and being closely spaced, for example with aspacing between neighboring nanowires smaller than the nanowire length,such as for example a spacing that is a factor of 1.2 to 10 smaller thanthe nanowire length. A relatively cheap method for manufacturing suchplurality of electrically conductive nanowires comprises electroplatingof a metal in a porous anodic aluminum oxide (AAO) template formed byanodization of an aluminum foil. Up to 100 micrometer thick porousaluminum oxide templates can be produced. However, the pores or channelsof the templates produced by anodization of aluminum foils are alwayscovered with an insulating aluminum oxide barrier layer having athickness of tens to hundreds of nanometers. This barrier layer may beremoved from the channel bottoms to enable subsequent formation of theplurality of electrically conductive nanowires by electroplating.

Various methods exist for removing the barrier layer from the channelbottoms, without separation of the template from the underlyingremaining part (non-anodized part) of the aluminum foil. For example,the voltage used in the anodization process may be gradually reducedduring the final stage of anodization. This results in a reduction ofthe interpore distance and of the pore size at a bottom of the channels,with a barrier layer of smaller thickness, for example 1 nm or less.Such barrier layer thickness is sufficiently small to allowelectroplating of a metal inside the channels or pores. However, thisapproach results in nanowires poorly connected to the substrate, throughlong (hundreds of nanometers long) root-like, thin (a few nm indiameter) nanowires. This may result in poor mechanical stability of thenanowires network, prone to delamination from the substrate.

Another method for removing the barrier layer from the channel bottomsof the template comprises thinning the barrier layer by immersing thetemplate in a H₃PO₄ solution that slowly etches the barrier layer. This,however, results in excessive pore widening, resulting in nanowiresformed in such a template that have a rather large diameter and thatfill most of the volume. This limits the volume remaining available forthe active electrode material to be coated thereon, eventually limitingthe energy density of the electrode.

Yet another method for removing the barrier layer from the channelbottoms of the template comprises separation of the template from theunderlying remaining part (non-anodized part) of the aluminum foil.According to this method, the aluminum foil is removed, e.g. dissolved,after formation of the porous template. This results in a fragile, freestanding template with an exposed barrier layer at one side and openpores at another side. The exposed barrier layer is then removed, forexample by single-side etching in a diluted H₃PO₄ solution, and a thinmetal layer is deposited to act as a working electrode for subsequentelectrodeposition of metallic nanowires in the template. However, thefragility of the free-standing template makes this method hard toimplement in large-scale manufacturing.

Hence, there may be use for a method that allows removing the barrierlayer from the channel bottoms of a porous anodic template forsubsequent formation therein of a plurality of spaced nanowires e.g. byelectroplating, wherein pore widening is avoided at one hand, whereinpore narrowing is avoided on the other hand, and wherein the method issuitable for implementation in large-scale manufacturing.

In a method for fabricating solid-state batteries having athree-dimensional electrode structure, there may be a formation step forforming an active electrode material layer on the three-dimensionalelectrode structure. The active electrode material layer may be formedby a process that allows conformal deposition. A method that can be usedis electroplating. For example, in case of Li ion insertion electrodes,manganese oxide (MnO_(x) with 1≤x≤2) may be used as a cathode precursormaterial, which is then further transformed into an active lithiummanganese oxide (LMO) electrode material upon conversion with lithium(lithiation).

In large-scale manufacturing of commercial batteries, a hot acidic bathcontaining MnSO₄ and H₂SO₄ is typically used for the synthesis ofMnO_(x). However, due to the acidic nature of the bath,electrodeposition cannot be carried out on most metals, due to theirinherent oxidation and dissolution in an acidic environment uponapplication of an anodic current. The only metals suitable for anodicdeposition of MnO₂ from acidic baths are the noble metals such as Pt orAu or metals forming a stable, dense passive oxide layer on theirsurface, such as titanium. However, these metals are either veryexpensive (noble metals) or very difficult to electrodeposit (titanium).

Other methods for the fabrication of manganese oxide cathode precursorsuse neutral manganese baths based on organic complexes of Mn²⁺, such asacetates or citrates. These baths, having a pH close to 7, can be usedto electroplate MnO_(x) precursors on less noble metals, such as Ni.However, due to the near-neutral pH of such baths and due to thepresence of dissolved oxygen, these solutions are not stable and, upontime, MnO_(x) precipitates are formed in the bath. This substantiallylimits the applicability of these baths for large-scale manufacturing,where stability of the baths is important from an economical andindustrial point of view. The change in composition of the bath may alsolead to changes in electroplating kinetics, resulting in poorreproducibility.

Further, in a method for fabricating solid-state batteries an annealingstep (lithiation step) is typically done after deposition of the cathodeprecursor material on the electrode structure, to thereby activate(lithiate) the cathode precursor material and form an active (lithiated)cathode material. When using a non-noble metal such as for example atransition metal for forming the electrode structure, such annealingstep may lead to thermal degradation (e.g. due to oxidation or anotherchemical reaction) of the electrode structure.

Hence, there may use for a method that allows forming a layer of activeelectrode material on a broad range of metals, wherein the method may bea low-cost process suitable for large-scale manufacturing and whereinthe method allows substantially conformal deposition. Further, there maybe use for a method with a reduced risk of degradation of the electrodematerial during subsequent processing, such as annealing.

SUMMARY

Embodiments of the present disclosure provide anodization based methodsfor transforming at least part of a metal layer, more in particular atleast part of a valve metal layer, into a template comprising aplurality of spaced channels, e.g. a plurality of spaced nanochannels,wherein barrier layers resulting from the anodization process may beremoved with no or limited pore widening at one hand and with no orlimited pore narrowing on the other hand. Embodiments of the presentdisclosure provide templates obtainable by such methods.

The present disclosure provides methods for forming a plurality ofspaced structures, e.g. nanostructures, within the plurality of spacedchannels, e.g. nanochannels, of such templates, wherein the plurality ofspaced structures has mechanical stability. The present disclosureprovides methods for forming a plurality of spaced electricallyconductive structures, e.g. electrically conductive nanostructures,within the plurality of spaced channels, e.g., nanochannels, of suchtemplates, wherein an electrical contact is established between theplurality of spaced electrically conductive structures and an underlyingelectrically conductive substrate. The present disclosure providesdevices comprising such plurality of spaced structures.

The above features are at least partially provided by methods anddevices according to the present disclosure.

According to a first aspect, the present disclosure is related to amethod for transforming at least part of a valve metal layer into atemplate comprising a plurality of spaced channels alignedlongitudinally along a first direction. A method according to the firstaspect of the present disclosure comprises a first anodization stepanodizing at least part of the valve metal layer in the thicknessdirection and thereby forming a porous layer of valve metal oxidecomprising a plurality of channels, each channel having channel wallsaligned longitudinally along the first direction and having a channelbottom, the channel bottoms being coated with a first insulating metaloxide barrier layer as a result of the first anodization step; next aprotective treatment inducing hydrophobic surfaces to the channel wallsand channel bottoms; a second anodization step after the protectivetreatment, thereby substantially removing the first insulating metaloxide barrier layer from the channel bottoms and inducing anodizationonly at the bottoms of the plurality of channels and creating a secondinsulating metal oxide barrier layer at the channel bottoms; and anetching step in an acidic etching solution or in a basic etchingsolution, thereby removing the second insulating metal oxide barrierlayer from the channel bottoms. The plurality of spaced channels may forexample comprise a plurality of spaced nanochannels.

In the context of the present disclosure, a valve metal is a metalselected from the group of aluminum, tungsten, titanium, tantalum,hafnium, niobium, vanadium, and zirconium. In the context of the presentdisclosure, a valve metal layer is a layer comprising a valve metal or avalve metal alloy. A valve metal layer may be a single layer or it maybe a layer stack comprising at least two valve metal layers. In someembodiments of a method of the first aspect of the present disclosure avalve metal layer comprising a layer of aluminum, an aluminum alloy,titanium, a titanium alloy, tantalum, or a tantalum alloy may be used.

In embodiments of a method of the first aspect, performing theprotective treatment may comprise annealing at a temperature in therange between 300° C. and 550° C.

In embodiments of a method of the first aspect, performing theprotective treatment may comprise depositing a protective layer over thechannel walls and over the channel bottoms. In such embodiments, thesecond anodization step additionally removes the protective layer onlyfrom the channel bottoms.

Some embodiments of the method of the first aspect of the presentdisclosure may allow for the removal of a barrier layer from the channelbottoms of a template formed by anodization, wherein the barrier layercan be removed with a limited pore widening at one hand and with alimited pore narrowing on the other hand. This results in a templatecomprising a plurality of spaced channels having a diameter that issubstantially constant along their entire length, i.e. up to the bottom.

A limited pore narrowing may allow for an after-formation of a pluralityof structures inside the plurality of channels with mechanicalstability, a limited risk of delamination from an underlying substrate,and with an electrical and mechanical contact with the underlyingsubstrate, for example an electrically conductive underlying substrate.

A limited pore widening may result in a template comprising a pluralityof spaced channels having a diameter (corresponding to a final porediameter) that is smaller than, e.g. substantially smaller than, aspacing between neighboring channels (wherein the spacing is definedhere as a distance between facing channel walls). This may allow for theafter-formation of a plurality of structures inside the plurality ofchannels of the template that take in a reduced volume as compared toalternate templates where pore widening results in channels being spacedat a distance that is typically smaller than their diameter. A pluralityof structures taking in a reduced volume may result in an increasedvolume remaining available between the structures, e.g. for depositionof an additional layer or additional layers. For example, a plurality ofstructures formed inside the plurality of channels may be used as acurrent collector in electrochemical devices such as for exampleelectrochemical sensors, batteries, supercapacitors, fuel cells,(photo)electrolyzers, or chemical reactors. The increased volumeavailable between the structures may then for example be utilized forproviding a layer of functional material, such as a layer of activeelectrode material or an electrolyte material, the present disclosurenot being limited thereto.

A method of the first aspect of the present disclosure may be relativelystraightforward. It does not require sophisticated equipment or vacuumequipment and it is therefore potentially low-cost. It is suitable forimplementation in large-scale manufacturing.

A method of the first aspect of the present disclosure, through the useof an anodization based process for forming the template, may allow forcontrol of a diameter of the plurality of spaced channels and a distancebetween neighboring channels by controlling a voltage or a current usedduring anodization. A method of the first aspect of the presentdisclosure, through the use of an anodization based process for formingthe template, may allow for control of a depth of the plurality ofspaced channels by controlling a duration of the first anodization step.

In embodiments of a method of the first aspect wherein performing theprotective treatment comprises depositing a protective layer on thechannel walls and on the channel bottoms, the protective layer may forexample comprise hydrophobic silane or a polymer that is resistant tothe etching solution, such as for example polystyrene, poly(methyl2-methylpropanoate), or poly(dimethylsiloxane).

In embodiments of a method of the first aspect of the present disclosurethe etching solution may be an aqueous solution, which may allow thetemplate to be formed without the use of organic solvents, resulting inan environmentally friendly method. The aqueous etching solution may forexample be an acidic etching solution comprising phosphoric acid,sulfuric acid, oxalic acid or chromic acid or a combination thereof.Alternatively, the etching solution may be a basic etching solution e.g.comprising ammonia, hydrogen peroxide, potassium hydroxide, or acombination thereof.

In embodiments of a method of the first aspect the etching solution mayfurther comprise a surface tension adjusting agent, where the surfacetension adjusting agent may facilitate penetration of the etchingsolution inside the plurality of channels towards the channel bottoms.The surface tension adjusting agent may for example be selected fromethyl alcohol, isopropyl alcohol, acetone, and sodium dodecyl sulphate,the present disclosure not being limited thereto.

Embodiments of a method of the first aspect of the present disclosuremay further comprise providing ultrasonic waves during the secondanodization step, which may facilitate removal of the first insulatingmetal oxide barrier layer and, if present, removal of the protectivelayer, from the channel bottoms during the second anodization step. Itmay further facilitate removal of the second insulating metal oxidebarrier layer from the channel bottoms during the etching step.Embodiments of a method of the first aspect of the present disclosuremay comprise providing ultrasonic waves during the first anodizationstep. Embodiments of a method of the first aspect of the presentdisclosure may comprise providing ultrasonic waves during both the firstanodization step and the second anodization step.

In embodiments of a method of the first aspect of the present disclosurethe first anodization step may anodize only a part of the valve metallayer in the thickness direction, to thereby form the template anddefining a substrate supporting the template, wherein the substratecomprises a remaining, non-anodized part of the valve metal layer. Thismay allow the formation of templates from a free-standing metal layersuch as a free-standing metal foil, e.g. a free-standing aluminum foil.In such embodiments, the need for providing a separate substratesupporting the valve metal layer may be reduced, which may lead to areduced cost. Using a free-standing layer of metal may allow theanodization of the layer at two opposite sides or surfaces, thusallowing the formation of a stack comprising a first porous layer ofvalve metal oxide (first template), a non-anodized valve metal layer(substrate) and a second porous layer of valve metal oxide (secondtemplate). Such a stack comprising a first template and a secondtemplate at opposite substrate sides may for example be used for forminga plurality of spaced (nano)structures in a fabrication process ofsolid-state batteries comprising a stack of battery cells. In suchembodiments, a single substrate may provide support for nanostructures(the nanostructures e.g. having the function of a current collector) atboth sides of the substrate, thus reducing the volume occupied bysubstrate material per battery cell.

In other embodiments of a method of the first aspect of the presentdisclosure the valve metal layer may be provided on an electricallyconductive substrate. In this context, “electrically conductivesubstrate” also includes any substrate comprising an electricallyconductive layer at an exposed surface thereof. In such embodiments, thefirst anodization step may anodize the valve metal layer throughout thelayer in the thickness direction, to thereby form a porous layer ofvalve metal oxide comprising a plurality of channels, each channelhaving channel walls aligned longitudinally along the first directionand having a channel bottom, the channel bottoms being located at aninterface between the valve metal layer and the underlying electricallyconductive layer or substrate. In such embodiments, the etching stepexposes the electrically conductive layer at the channel bottoms. Theelectrically conductive layer may for example be a titanium nitridelayer, a titanium layer, a nickel layer, an indium tin oxide layer, agold layer, or a platinum layer, the present disclosure not beinglimited thereto.

According to a second aspect, the present disclosure is related to atemplate comprising a plurality of spaced channels alignedlongitudinally along a first direction, wherein the template isobtainable by a method according to an embodiment of the first aspect ofthe present disclosure.

In general, features of the second aspect of the present disclosureprovide similar advantages as discussed above in relation to the firstaspect of the present disclosure.

In embodiments of the template of the second aspect of the presentdisclosure, the plurality of spaced channels may have a diameter that issubstantially constant along their entire length, i.e. up to the bottom,and that they may have a channel bottom free of any barrier layer, i.e.exposing an underlying substrate. This may allow for the after-formationof a plurality of structures inside the plurality of channels withmechanical stability, a limited risk of delamination from an underlyingsubstrate, and with an electrical and mechanical contact with theunderlying substrate, for example an electrically conductive underlyingsubstrate.

In some embodiments of the template of the second aspect of the presentdisclosure, the plurality of spaced channels may have a diameter that issmaller than, e.g. substantially smaller than, a spacing betweenneighboring channels (wherein the spacing is defined here as a distancebetween facing channel walls). This may allow the after-formation of aplurality of structures inside the plurality of channels of the templatethat take in a reduced volume as compared to alternate templates whereinpore widening results in channels being spaced at a distance that istypically smaller than their diameter. A plurality of structures takingin a reduced volume may allow an increased volume to remain availablebetween the structures, e.g. for deposition of an additional layer oradditional layers. For example, a plurality of structures formed insidethe plurality of channels may be used as a current collector inelectrochemical devices such as electrochemical sensors, batteries,supercapacitors, fuel cells, (photo)electrolyzers, or chemical reactors.The increased volume available between the structures may then forexample be utilized for providing a layer of functional material, suchas for example a layer of active electrode material or an electrolytematerial, the present disclosure not being limited thereto.

In embodiments of a template of the second aspect of the presentdisclosure, the first direction may be at an angle in the range between60° and 90°, for example between 80° and 90°, with respect to a surfaceof the valve metal layer from which the template is formed. For example,the first direction may be substantially orthogonal to a surface of thevalve metal layer.

In embodiments of a template of the second aspect of the presentdisclosure, the template may further comprise a plurality ofinterconnecting channels oriented along a second direction differentfrom the first direction, wherein the interconnecting channels form aconnection between neighboring spaced channels oriented along the firstdirection. The second direction may for example be substantiallyorthogonal to the first direction. A template that includes suchinterconnecting channels may allow for the after-formation of aplurality of interconnected structures inside the plurality of channelsof the template. Such plurality of interconnected structures may forexample form a mesh-shaped structure.

According to a third aspect, the present disclosure is related to amethod for forming a plurality of spaced structures on a substrate. Amethod according to the third aspect of the present disclosure comprisestransforming at least part of a valve metal layer into a templatecomprising a plurality of spaced channels aligned longitudinally along afirst direction according to an embodiment of the first aspect of thepresent disclosure, thereby forming the template and defining thesubstrate, and depositing a solid functional material within thechannels of the template to thereby form the plurality of spacedstructures inside the plurality of spaced channels. This results in aplurality of spaced structures being aligned longitudinally along thefirst direction. The method may further comprise removing the templateby etching. Examples of spaced electrically conductive structures thatmay be formed using a method of the third aspect of the presentdisclosure are pillars, nanopillars, wires, nanowires, tubes (or“hollow” wires), nanotubes, meshes, and nanomeshes.

In the context of the third aspect of the present disclosure, afunctional material or functional material layer is a material ormaterial layer that satisfies or provides a defined functionality and/orhas defined properties, adjusted for a device in which it is integrated.

In embodiments of a method of the third aspect of the presentdisclosure, depositing the solid functional material within the channelsof the template may comprise depositing an electrically conductivematerial, a semiconductor material, an electrically insulating materialor a combination thereof.

In embodiments, depositing the solid functional material within thechannels of the template may comprise filling the channels with thesolid functional material, e.g. completely filling the channels in alateral direction orthogonal to the first direction. In embodiments,depositing the solid functional material within the channels maycomprise depositing a layer of solid functional material on the channelwalls, thereby only partially filling the channels in a lateraldirection with the solid functional material and leaving openingsinside.

In embodiments of a method of the third aspect of the presentdisclosure, depositing the solid functional material within the channelsof the template may comprise depositing an electrically conductivematerial by galvanostatic or potentiostatic electrodeposition orplating, to thereby form a plurality of spaced electrically conductivestructures. In such embodiments, a low-resistance electrical contact maybe established between the plurality of spaced electrically conductivestructures and an underlying electrically conductive substrate. Theelectrical contact may for example have a contact resistance lower than1 Ohm cm².

In general, features of the third aspect of the present disclosureprovide similar advantages as discussed above in relation to theprevious aspects of the present disclosure.

A method of the third aspect of the present disclosure may allow theformation of a plurality of spaced structures on a substrate withmechanical stability, a limited risk of delamination from the underlyingsubstrate, and a mechanical contact with the underlying substrate. Amethod of the third aspect of the present disclosure may allow theformation of a plurality of spaced electrically conductive structureswith an electrical contact to an underlying electrically conductivesubstrate, such as for example with a contact resistance lower than 1Ohm cm². A method of the third aspect of the present disclosure mayallow for the formation of a plurality of spaced structures, e.g.electrically conductive structures, taking in a relatively limitedvolume, thereby leaving an increased volume available in between theplurality of spaced structures, for example for deposition of anadditional layer, e.g. an additional layer of functional material, suchas e.g. a layer of active electrode material.

A method of the third aspect of the present disclosure may be relativelystraightforward. It does not require sophisticated equipment or vacuumequipment and is therefore potentially low-cost. It is suitable forimplementation in large-scale manufacturing.

A method of the third aspect of the present disclosure may allow forcontrol of a diameter and a length (height) of the plurality of spacedstructures, e.g. electrically conductive structures, and of a distancebetween neighboring structures. This may further enable control of theenergy density and power density of a battery cell having a currentcollector comprising such a plurality of spaced electrically conductivestructures.

In embodiments of the method of the third aspect of the presentdisclosure the electrically conductive material deposited within thechannels of the template to thereby form the plurality of spacedelectrically conductive structures may be a transition metal, which mayresult in a reduced cost. Further, this may allow a reduction in cost ofbattery cells having a current collector comprising such plurality ofspaced electrically conductive transition metal structures. Inembodiments of the third aspect of the present disclosure the transitionmetal may for example be selected from nickel, copper, and chromium.

According to a fourth aspect, the present disclosure is related to anentity comprising a substrate with a plurality of spaced structuresthereon, the plurality of spaced structures being aligned longitudinallyalong a first direction and being obtainable by a method according to anembodiment of the third aspect of the present disclosure.

In general, features of the fourth aspect of the present disclosureprovide similar advantages as discussed above in relation to theprevious aspects of the present disclosure.

In embodiments of an entity of the fourth aspect of the presentdisclosure the first direction may be at an angle in the range between60 and 90, for example between 80 and 90, with respect to a surface ofthe substrate. For example, the first direction may be substantiallyorthogonal to a surface of the substrate.

In embodiments of an entity of the fourth aspect of the presentdisclosure, the entity may further comprise a plurality ofinterconnecting structures oriented along a second direction differentfrom the first direction, wherein the interconnecting structures form aconnection between neighboring spaced structures oriented along thefirst direction, thereby forming for example a mesh-shaped structure.The second direction may for example be substantially orthogonal to thefirst direction, the present disclosure not being limited thereto.

In embodiments of the fourth aspect of the present disclosure theplurality of spaced structures and, if present, the plurality ofinterconnecting structures, may comprise an electrically conductivematerial, a semiconductor material, an electrically insulating materialor a combination thereof.

According to a fifth aspect, the present disclosure is related to adevice comprising an entity according to the fourth aspect of thepresent disclosure. In embodiments of the fifth aspect of the presentdisclosure the device may for example be an electrochemical device, suchas e.g. an electrochemical sensor, a battery, a supercapacitor, a fuelcell, an electrolyzer, a photo-electrolyzer, or a chemical reactor, thepresent disclosure not being limited thereto.

In general, features of the fifth aspect of the present disclosureprovide similar advantages as discussed above in relation to theprevious aspects of the present disclosure.

According to a sixth aspect, the present disclosure is related to amethod for forming a layer of a functional material on an electricallyconductive substrate, such as for example on a transition metalsubstrate. A method according to the sixth aspect of the presentdisclosure comprises depositing an interlayer on the substrate, whereinthe interlayer comprises a transition metal oxide, a noble metal, or anoble-metal oxide, and wherein the interlayer has a thickness in therange between 0.5 nm and 30 nm, for example in the range between 0.5 nmand 10 nm; depositing a functional material precursor layer on theinterlayer; and activating the functional material precursor layer byannealing to thereby form the layer of functional material.

In embodiments of the method of the sixth aspect of the presentdisclosure the layer of functional material may for example be a layerof active electrode material. In such embodiments depositing thefunctional material precursor layer comprises depositing an electrodematerial precursor layer. The annealing step for activating theelectrode material precursor layer may be done in the presence of an ioncontaining precursor, such as for example a lithium containingprecursor, a sodium containing precursor, or a magnesium containingprecursor, the present disclosure not being limited thereto. Inembodiments of the sixth aspect of the present disclosure the electrodematerial may be a cathode material or an anode material. The functionalmaterial precursor layer may be a layer of cathode precursor material,for example comprising manganese oxide, manganese dioxide, cobalt oxide,manganese nickel oxide, or iron phosphate, or it may be a layer of anodeprecursor material.

In general, features of the sixth aspect of the present disclosureprovide similar advantages as discussed above in relation to theprevious aspects of the present disclosure.

Providing an interlayer in accordance with a method of the sixth aspectof the present disclosure may result in a reduced risk of degradation ofthe underlying electrically conductive substrate material, such as forexample a reduced risk of oxidation of the electrically conductivesubstrate material. The electrically conductive substrate may forexample be used as a current collector of a battery cell. Providing aninterlayer in accordance with a method of the sixth aspect of thepresent disclosure may result in a reduced risk of degradation (e.g.oxidation) of the current collector material, for example under theinfluence of the step of activating the layer of electrode precursormaterial by annealing.

Providing an interlayer in accordance with a method of the sixth aspectof the present disclosure that it may result in a reduced risk ofdegradation of the underlying electrically conductive substratematerial, e.g. current collector material, under the influence of anelectrochemical deposition process, as may for example be used fordepositing the functional material precursor layer. Such electrochemicaldeposition process may for example comprise deposition in an acidicbath, for example for depositing the layer of electrode precursormaterial (electrode material precursor layer), the present disclosurenot being limited thereto.

In embodiments of the sixth aspect of the present disclosure depositingthe functional material precursor layer, e.g. layer of electrodeprecursor material, may comprise anodic electrodeposition from an acidicsolution or from a basic solution, where anodic electrodeposition may bea low-cost process suitable for large-scale manufacturing. In someembodiments, the use of an acidic solution may offer a stability of theelectrodeposition bath.

A method of the sixth aspect of the present disclosure may allow for theformation of a functional material layer, such as a layer of activeelectrode material, on a broad range of metals, including for examplerelatively cheap transition metals. This further allows for examplereducing a cost of battery cells having a current collector structurecomprising such plurality of spaced electrically conductive transitionmetal structures.

A method of the sixth aspect of the present disclosure may allow for theconformal formation of a layer of functional material on a variety ofmetal substrates, including transition metal substrates, for example onthree-dimensional transition metal substrates. More in particular, amethod of the sixth aspect of the present disclosure may allow for theconformal formation of a layer of active cathode material on a varietyof metal substrates, including transition metal substrates, for exampleon three-dimensional transition metal substrates Compared to fabricationmethods where an active anode material is formed on a three-dimensionalsubstrate, the method of the sixth aspect of the present disclosure maymay allow for the fabrication of solid-state battery cells with animproved energy density and power density. This is related to agenerally lower capacity of cathode materials as compared to anodematerials. Therefore, three-dimensional structuring of a cathode layermay increase the capacity, energy density, and/or power density of abattery cell as compared to an approach where only the anode layer isthree-dimensionally structured and not the cathode layer.

In embodiments of the sixth aspect of the present disclosure theelectrically conductive substrate may be a three-dimensional substratecomprising a plurality of spaced electrically conductive structuresbeing substantially aligned along a first direction, which may result ina substantially increased electrode surface area as compared to flatsubstrates, which may further lead to substantially higher chargingrates of solid-state battery cells comprising such three-dimensionalelectrode structure. In embodiments of the sixth aspect of the presentdisclosure the electrically conductive substrate may further comprise aplurality of electrically conductive interconnecting structures orientedalong a second direction different from the first direction, such as forexample substantially orthogonal to the first direction, wherein theelectrically conductive interconnecting structures form a connectionbetween neighboring electrically conductive structures oriented alongthe first direction.

Examples of spaced electrically conductive structures are pillars,nanopillars, wires, nanowires, tubes (or “hollow” wires), nanotubes,meshes, and nanomeshes. Such structures may enable the formation offlexible battery cells, due to a reduced mechanical stress upon bending.

In embodiments of the sixth aspect of the present disclosure wherein theinterlayer comprises a transition metal oxide, depositing the interlayermay for example comprise electrodeposition in a solution having a pH inthe range of 7 to 12. The use of a neutral or basic solution fordepositing the interlayer on the substrate, e.g. transition metalsubstrate, may allow for the formation of the interlayer with a reducedrisk of degradation of the substrate, e.g. transition metal substrate,under the influence of the interlayer deposition process. Using anelectrodeposition process for depositing the interlayer may be suitablefor low-cost, large-scale manufacturing. The transition metal oxide mayfor example comprise chromium oxide, nickel oxide, titanium oxide, ormanganese oxide.

According to a seventh aspect, the present disclosure is related to amethod for fabricating a solid-state battery cell. A method according tothe seventh aspect of the present disclosure comprises forming aplurality of spaced electrically conductive structures on a substrateaccording to a method of the third aspect of the present disclosure;forming a first layer of active electrode material on the plurality ofelectrically conductive structures, wherein the first layer of activeelectrode material conformally coats surfaces of the plurality ofelectrically conductive structures; depositing a solid electrolyte layerover the first layer of active electrode material; and forming a secondlayer of active electrode material over the solid electrolyte layer,wherein one of the first layer of active electrode material and thesecond layer of active electrode material forms a cathode layer and theother one forms an anode layer of the solid-state battery cell. Theplurality of spaced electrically conductive structures may form a firstcurrent collector of the solid-state battery cell. The method mayfurther comprise depositing a second current collector or collectorlayer over the second layer of active electrode material.

In embodiments of the method of the seventh aspect of the presentdisclosure forming the first layer of active electrode material on theplurality of electrically conductive structures may be done according toan embodiment of the sixth aspect of the present disclosure.

In general, features of the seventh aspect of the present disclosureprovide similar advantages as discussed above in relation to theprevious aspects of the present disclosure.

A method of the seventh aspect of the present disclosure may allow asubstantial part of the fabrication steps to be done using astraightforward, low-cost electrochemical deposition process. More inparticular, the anodization steps in the method for forming a template,the step of depositing an electrically conductive material within thetemplate and the step of depositing an electrode material precursorlayer may be done using an electrochemical deposition process. Thesesteps may be done in the same equipment. A method of the seventh aspectof the present disclosure may include electrochemical depositionprocesses that may be performed in an aqueous solution without organicsolvents, resulting in an environmental-friendly fabrication method.

According to an eighth aspect, the present disclosure is related to amethod for fabricating a solid-state battery cell. A method according tothe eighth aspect of the present disclosure comprises: forming aplurality of spaced electrically conductive structures on a substrate;forming a first layer of active electrode material on the plurality ofspaced electrically conductive structures in accordance with anembodiment of the sixth aspect of the present disclosure, wherein thefirst layer of active electrode material conformally coats surfaces ofthe plurality of spaced electrically conductive structures; depositing asolid electrolyte layer over the first layer of active electrodematerial; and forming a second layer of active electrode material overthe solid electrolyte layer, wherein one of the first layer of activeelectrode material and the second layer of active electrode materialforms a cathode layer and the other one forms an anode layer of thesolid-state battery cell. The plurality of spaced electricallyconductive structures may form a first current collector layer of thesolid-state battery cell. The method may further comprise depositing asecond current collector layer over the second layer of active electrodematerial.

In general, features of the eighth aspect of the present disclosureprovide similar advantages as discussed above in relation to theprevious aspects of the present disclosure.

According to a ninth aspect, the present disclosure is related to amethod for fabricating a solid-state battery. A method according to theninth aspect of the present disclosure comprises: fabricating aplurality of solid-state battery cells in accordance with an embodimentof the seventh or the eighth aspect of the present disclosure; andforming a stack of the plurality of solid-state battery cells with asolid electrolyte being provided in between neighboring solid-statebattery cells.

In general, features of the ninth aspect of the present disclosureprovide similar advantages as discussed above in relation to theprevious aspects of the present disclosure.

According to a tenth aspect, the present disclosure is related to asolid-state battery cell. A solid-state battery cell according to thetenth aspect of the present disclosure comprises a plurality of spacedelectrically conductive structures; a first layer of active electrodematerial conformally coating surfaces of the plurality of spacedelectrically conductive structures; a solid electrolyte layer over thefirst layer of active electrode material; a second layer of activeelectrode material over the solid electrolyte layer, wherein one of thefirst layer of active electrode material and the second layer of activeelectrode material forms a cathode layer and the other one forms ananode layer of the solid-state battery cell; and a 0.5 nm to 10 nm thickinterlayer between the plurality of electrically conductive structuresand the first layer of active electrode material, wherein the interlayercomprises a transition metal oxide, a noble metal, or a noble-metaloxide. In embodiments of the tenth aspect of the present disclosure theplurality of spaced electrically conductive structures may form a firstcurrent collector layer of the solid-state battery cell. The solid-statebattery cell may further comprise a second current collector layer overthe second layer of active electrode material.

In general, features of the tenth aspect of the present disclosureprovide similar advantages as discussed above in relation to theprevious aspects of the present disclosure.

According to an eleventh aspect, the present disclosure is related to asolid-date battery comprising at least one, for example a plurality of,e.g. a stack of, solid-state battery cells according to the tenth aspectof the present disclosure.

In general, features of the eleventh aspect of the present disclosureprovide similar advantages as discussed above in relation to theprevious aspects of the present disclosure.

Particular aspects of the disclosure are set out in the accompanyingindependent and dependent claims. Features from the dependent claims maybe combined with features of the independent claims and with features ofother dependent claims as appropriate and not merely as explicitly setout in the claims.

The above and other characteristics and features of the presentdisclosure will become apparent from the following detailed description,taken in conjunction with the accompanying drawings, which illustrate,by way of example, the principles of the disclosure. This description isgiven for the sake of example only, without limiting the scope of thedisclosure. The reference figures quoted below refer to the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example process sequence of a method fortransforming at least part of a valve metal layer into a templatecomprising a plurality of spaced (nano)channels according to anembodiment of the first aspect of the present disclosure.

FIG. 2 schematically shows a cross section illustrating results of astep of the process sequence of FIG. 1.

FIG. 3 schematically shows a cross section illustrating results of astep of the process sequence of FIG. 1.

FIG. 4 schematically shows a cross section illustrating results of astep of the process sequence of FIG. 1.

FIG. 5 schematically shows a cross section illustrating results of astep of the process sequence of FIG. 1.

FIG. 6 schematically shows a cross section illustrating results of astep of the process sequence of FIG. 1.

FIG. 7 schematically shows a cross section of an example of a templateaccording to an embodiment of the second aspect of the presentdisclosure.

FIG. 8 schematically shows a cross section of an example of a templateaccording to an embodiment of the second aspect of the presentdisclosure.

FIG. 9 illustrates an example process sequence of a method for forming aplurality of spaced (nano)structures on a substrate according to anembodiment of the third aspect of the present disclosure.

FIG. 10 schematically shows a cross section illustrating results of astep of the process sequence of FIG. 9.

FIG. 11 schematically shows a cross section of an example of an entityaccording to an embodiment of the fourth aspect of the presentdisclosure.

FIG. 12A schematically shows a cross section of an example of an entityaccording to an embodiment of the fourth aspect of the presentdisclosure.

FIG. 12B schematically shows a cross section of an example of an entityaccording to an embodiment of the fourth aspect of the presentdisclosure.

FIG. 13 illustrates an example process sequence of a method for forminga layer of functional material on an electrically conductive substrateaccording to an embodiment of the sixth aspect of the presentdisclosure.

FIG. 14 schematically shows a cross section illustrating results of astep of the process sequence of FIG. 13.

FIG. 15 schematically shows a cross section illustrating results of astep of the process sequence of FIG. 13.

FIG. 16 schematically shows a cross section illustrating results of astep of the process sequence of FIG. 13.

FIG. 17 shows potential transients as measured during galvanostaticdeposition of a MnO_(x) cathode precursor layer on Ni nano-mesh samples.The curves labeled (a) corresponds to samples without an interlayerbeing provided, whereas the curve labeled (b) corresponds to samplescovered with an interlayer in accordance with an embodiment of the thirdaspect of the present disclosure.

FIG. 18 shows results of a cyclic voltammetry experiment on a structurecomprising a nickel substrate with a MnO_(x) layer deposited thereon.Curves labeled (a) correspond to a structure without an interlayer beingprovided, whereas curves labeled (b) correspond to a structure having aninterlayer provided thereon before deposition of the MnO_(x) layer, inaccordance with an embodiment of the third aspect of the presentdisclosure.

FIG. 19 schematically shows a cross section of an example of asolid-state battery cell according to an embodiment of the tenth aspectof the present disclosure.

FIG. 20 schematically shows a cross section of an example of asolid-state battery according to an embodiment of the eleventh aspect ofthe present disclosure.

In the different figures, the same reference signs refer to the same oranalogous elements.

DETAILED DESCRIPTION

The present disclosure will be described with respect to particularembodiments and with reference to certain drawings but the disclosure isnot limited thereto but only by the claims. The drawings described areonly schematic and are non-limiting. In the drawings, the size of someof the elements may be exaggerated and not drawn on scale forillustrative purposes. The dimensions and the relative dimensions do notcorrespond to actual reductions to practice of the disclosure.

The terms first, second, third and the like in the description and inthe claims, are used for distinguishing between similar elements and notnecessarily for describing a sequence, either temporally, spatially, inranking or in any other manner. It is to be understood that the terms soused are interchangeable under appropriate circumstances and that theembodiments of the disclosure described herein are capable of operationin other sequences than described or illustrated herein.

It is to be noticed that the term “comprising”, used in the claims,should not be interpreted as being restricted to the means listedthereafter; it does not exclude other elements or steps. It is thus tobe interpreted as specifying the presence of the stated features,integers, steps or components as referred to, but does not preclude thepresence or addition of one or more other features, integers, steps orcomponents, or groups thereof. Thus, the scope of the expression “adevice comprising A and B” should not be limited to devices consistingonly of components A and B. It means that with respect to the presentdisclosure, the only relevant components of the device are A and B.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the present disclosure. Thus, appearances of the phrases“in one embodiment” or “in an embodiment” in various places throughoutthis specification are not necessarily all referring to the sameembodiment, but may. Furthermore, the particular features, structures orcharacteristics may be combined in any suitable manner, as would beapparent to one of ordinary skill in the art from this disclosure, inone or more embodiments.

Similarly it should be appreciated that in the description of exampleembodiments of the disclosure, various features of the disclosure aresometimes grouped together in a single embodiment, figure, ordescription thereof for the purpose of streamlining the disclosure andaiding in the understanding of one or more of the various inventiveaspects. This method of disclosure, however, is not to be interpreted asreflecting an intention that the claimed disclosure requires morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive aspects lie in less than allfeatures of a single foregoing disclosed embodiment. Thus, the claimsfollowing the detailed description are hereby expressly incorporatedinto this detailed description, with each claim standing on its own as aseparate embodiment of this disclosure.

Furthermore, while some embodiments described herein include some butnot other features included in other embodiments, combinations offeatures of different embodiments are meant to be within the scope ofthe disclosure, and form different embodiments, as would be understoodby those in the art. For example, in the following claims, any of theclaimed embodiments can be used in any combination.

In the description provided herein, numerous specific details are setforth. However, it is understood that embodiments of the disclosure maybe practiced without these specific details. In other instances,existing methods, structures and techniques have not been shown indetail in order not to obscure an understanding of this description.

The following terms are provided solely to aid in the understanding ofthe disclosure.

In the context of the present disclosure, a battery cell is a structurecomprising two electrode layers with an electrolyte layer in between,i.e. a structure comprising a stack of a first electrode layer (firstlayer of active electrode material)/electrolyte layer/second electrodelayer (second layer of active electrode material). The first electrodelayer and the second electrode layer are of opposite polarity. A batterymay comprise a single battery cell or it may comprise a plurality of,e.g. at least two, battery cells. A battery may comprise two or morebattery cells connected in series or in parallel, or a combination ofseries and parallel connected battery cells. A battery further comprisesa first current collector layer and a second collector layer, the firstcurrent collector layer and the second current collector layer being ofopposite polarity.

In the context of the present disclosure, an ion insertion battery cellis a battery cell comprising electrodes that can accept or releasecations or anions during operation of the battery cell. Ion insertionbattery cells can rely on the insertion/extraction of only one cationelement, multiple cation elements, only anions or a mixture of anion andcation elements. An ion insertion battery cell further comprises anelectrolyte that allows for ionic conduction of the respective ion used,while being (electro)chemically stable with regard to the used electrodematerials.

In a rechargeable battery cell, each of the electrodes has a firstpolarity during the discharge (i.e. battery operation) and a second,opposite polarity during charging. Technically speaking however, thenegative electrode is the anode during the discharge and the cathodeduring charging. Vice versa, the positive electrode is the cathodeduring discharge and the anode when charging the battery. In the contextof the present disclosure, the terminology of the discharge (i.e.battery operation) is used. Herein further, with anode the negativeelectrode is meant and with cathode the positive electrode is meant.Through the disclosure, when referred to “anode material” it is meantthe negative electrode material and when referred to “cathode material”it is meant the positive electrode material.

In the context of the present disclosure, an active electrode materialis a material that is a component of a battery electrode layer. In theactive electrode material, the actual electrochemical transformation(change in valence or oxidation state of the atoms) takes place, whichgives rise to storage of chemical energy in the electrode. An electrodelayer is typically composed of the active electrode material andsupporting material.

In the context of the present disclosure, the term “anodization” whenapplied to a valve metal (such as for example aluminum) or to a valvemetal layer refers to an electrochemical process comprising applying apotential or a current between the valve metal layer (the material to beanodized) functioning as a working electrode at one hand and acounter-electrode at the other hand, in the presence of an acidelectrolyte. This method leads to the formation of a porous layer ofvalve metal oxide comprising plurality of pores or channels, e.g. acluster of channels, arranged in an orderly fashion (e.g. hexagonally)perpendicularly to the surface of the layer. This cluster may bereferred to as an array, due to the orderly nature of the arrangement.

In the context of the present disclosure, a valve metal is a metal thatcan be oxidized using an anodization process (anodic oxidation) tothereby form a stable valve metal oxide. More in particular, in thecontext of the present disclosure, a valve metal is a metal selectedfrom the group of aluminum, tungsten, titanium, tantalum, hafnium,niobium, vanadium, and zirconium. In the context of the presentdisclosure, a valve metal layer is a layer comprising a valve metal or avalve metal alloy (or a “doped” valve metal). An example of an aluminumalloy that may for example be used in the context of the presentdisclosure is a copper doped aluminum layer, e.g. with a dopingconcentration in the range between 1% and 10%, the present disclosurenot being limited thereto.

In the context of the present disclosure, when referring to a substrate,the substrate may be a planar substrate or a non-planar, e.g.three-dimensional (3D) substrate. In the context of the presentdisclosure, a 3D substrate may for example comprise a plurality of 3Dfeatures, 3D structures, such as 3D micro- or nano-structures, such asfor example a plurality of micro-pillars or nano-pillars, a plurality ofmicrowires or nanowires or 3D (nano)meshes, (nano)tubes, and/or otherporous structures, such as for example porous anodized alumina. The 3Dfeatures may be present in a regular pattern, such as for example aregular array pattern, or they may be randomly distributed over thesubstrate.

In the context of the present disclosure, a plurality of spaced channelsrefers to a plurality of channels that are separated in space from oneanother, i.e. that are located at a distance from each other. Theplurality of spaced channels may be either completely separated fromeach other, e.g. by a surrounding medium, or they may be interconnected,for example partially interconnected, e.g. by a plurality ofinterconnecting channels through a surrounding medium. The plurality ofinterconnecting channels may for example have a longitudinal orientationsubstantially orthogonal to a longitudinal orientation of the pluralityof spaced channels.

In the context of the present disclosure, a template comprising aplurality of spaced channels aligned longitudinally along a directionmay refer to a template comprising a plurality of channels beingcompletely separated from each other or to a template comprising aplurality of channels that are interconnected, for example partiallyinterconnected by a plurality of interconnecting channels. Theinterconnecting channels may be oriented in a direction substantiallyorthogonal to the longitudinal direction of the plurality of spacedchannels. In the context of the present disclosure, a templatecomprising a plurality of spaced channels aligned longitudinally along adirection may refer to a template comprising two or more regionspositioned subsequently along the longitudinal direction, wherein atleast a first region comprises a plurality of completely separated(non-interconnected) spaced channels and wherein at least a secondregion comprises a plurality of interconnected spaced channels (beinginterconnected by interconnecting channels).

In the context of the present disclosure, a plurality of spacedstructures, e.g. nanostructures, aligned longitudinally along adirection refers to a plurality of structures, e.g. nanostructures, thatare located at a distance from each other. The plurality of(nano)structures may for example comprise (nano)pillars, (nano)wires,(nano)meshes, or (nano)tubes. The plurality of structures, e.g.nanostructures, may be either completely separated from each other, e.g.by a surrounding medium such as air or a solid material different fromthe (nano)structure material, or they may be interconnected, for examplepartially interconnected, e.g. by a plurality of interconnectingstructures, e.g. interconnecting nanostructures. The plurality ofinterconnecting (nano)structures may for example have a longitudinalorientation substantially orthogonal to a longitudinal orientation ofthe plurality of spaced (nano)structures. The interconnecting(nano)structures are typically made of the same material as the spaced(nano)structures themselves. In the context of the present disclosure, aplurality of spaced (nano)structures aligned longitudinally along adirection may refer to structure comprising two or more regionspositioned subsequently along the longitudinal direction, wherein atleast a first region comprises a plurality of spaced, completelyseparated (non-interconnected) (nano)structures and wherein at least asecond region comprises a plurality of spaced, interconnected(nano)structures (for example being interconnected by interconnecting(nano)structures).

In the context of the present disclosure, a functional material orfunctional material layer is a material or material layer that satisfiesor provides a defined functionality and/or has defined properties,adjusted for a device in which it is integrated. A functional materialmay for example comprise a metal, a metal alloy, a semiconductor, anoxide, a metal hydride, a ceramic material, a metal-organic crystal, apolymer, or an organic supramolecular solid, the present disclosure notbeing limited thereto. It provides a defined functionality or property,such as for example a high electrical conductivity, catalytic activitytowards chemical reactions, electrochemical activity towards ioninsertion, high optical absorbance, iridescence, photoluminescence, highmagnetic anisotropy, or piezoelectricity, the present disclosure notbeing limited thereto. This is adjusted for the final device or intendedfield of application in which it is used. A functional material or afunctional material layer may for example have the functionality of anelectrode, a current collector, a catalyst, an energy storage material,a light absorber, a photonic crystal, a light emitter, an informationstorage medium, an ion trap, or a gas absorber, the present disclosurenot being limited thereto.

The disclosure will now be described by a detailed description ofseveral embodiments of the disclosure. It is clear that otherembodiments of the disclosure can be configured according to theknowledge of persons skilled in the art without departing from thetechnical teaching of the disclosure, the disclosure being limited onlyby the terms of the appended claims.

According to a first aspect, the present disclosure is related to amethod for transforming at least part of a valve metal layer into atemplate comprising a plurality of spaced (nano)channels alignedlongitudinally along a first direction. An example of a method accordingto an embodiment of the first aspect of the present disclosure isschematically illustrated in FIG. 1, showing a flow chart comprising anexample process sequence and in FIG. 2 to FIG. 8, schematically showingcross sections illustrating results of successive steps of the processsequence of FIG. 1.

As illustrated in the example shown in FIG. 1, a method 100 according toan embodiment of the first aspect of the present disclosure comprises afirst anodization step 101 of at least part of a valve metal layer, thefirst anodization step 101 resulting in the formation of a porous layerof valve metal oxide comprising a plurality of aligned spaced(nano)channels having bottom surfaces coated with a first insulatingmetal oxide barrier. The plurality of (nano)channels formed as a resultof the first anodization step are substantially aligned longitudinallyalong a first direction. The plurality of (nano)channels each have(nano)channel walls substantially aligned longitudinally along the firstdirection and a (nano)channel bottom substantially parallel with asurface of the valve metal layer. As a result of the first anodizationstep the surfaces of the (nano)channel bottoms are covered with a firstinsulating metal oxide barrier layer, for example a first valve metaloxide barrier layer.

In embodiments of the first aspect of the present disclosure the valvemetal layer may be a free-standing layer, for example a flexiblefree-standing layer such as a metal foil, or the valve metal layer maybe provided on a substrate, for example on a rigid substrate or on aflexible substrate. FIG. 2 illustrates an example of an embodimentwherein the valve metal layer 11 is a free-standing layer, but thepresent disclosure is not limited thereto. The first anodization step101 may result in a structure as schematically shown in FIG. 3. Itillustrates formation of a porous layer 12 of anodized metal comprisinga plurality of spaced (nano)channels 13 that are substantially alignedlongitudinally along a first direction. In embodiments of the presentdisclosure the first direction may correspond to a thickness directionof the valve metal layer, i.e. it may be substantially orthogonal to asurface of the valve metal layer, as schematically illustrated in theexample shown in FIG. 3. However, the present disclosure is not limitedthereto, and the first direction may be at an angle, for example at anangle in the range between 60° and 90°, with respect to a surface of thevalve metal layer. FIG. 3 illustrates an example wherein the firstdirection is orthogonal to the surface of the valve metal layer 11. Inother words, the first direction corresponds to a thickness direction Yof the valve metal layer 11. The plurality of (nano)channels 13 eachhave (nano)channel walls 14 substantially aligned longitudinally alongthe thickness direction Y and a (nano)channel bottom 15. As a result ofthe first anodization step 101 the surface of the (nano)channel bottoms15 is covered with a first insulating metal oxide barrier layer 21, asshown more in detail in the inset of FIG. 3.

In the example illustrated in FIG. 3 the porous layer 12 comprising theplurality of channels 13 is formed only in a part of the valve metallayer. However, the present disclosure is not limited thereto. Forexample, in embodiments according to the first aspect wherein the valvemetal layer 11 is provided on a substrate (not illustrated) the porouslayer 12 comprising the plurality of (nano)channels 13 may also beformed throughout the valve metal layer 11, thereby exposing theunderlying substrate at the channel bottoms.

In embodiments of the present disclosure (not illustrated) the firstanodization step may comprise complete immersion of a free-standingvalve metal layer 11 in an anodizing solution. In such embodiments, thefirst anodization step may result in the formation of a first porouslayer of valve metal oxide comprising a plurality of spaced(nano)channels at a first side of the valve metal layer andsimultaneously in the formation of a second porous layer of valve metaloxide comprising a plurality of spaced (nano)channels at a second,opposite side of the valve metal layer. In between the first porouslayer and the second porous layer a non-anodized valve metal layerremains.

A method 100 according to embodiments of the first aspect of the presentdisclosure comprises, after the first anodization step 101, performing aprotective treatment 102 (FIG. 1). The protective treatment induceshydrophobic surfaces to the (nano)channel walls 14 and (nano)channelbottoms 15, i.e. it results in (nano)channels 13 having hydrophobic(nano)channel wall surfaces and hydrophobic (nano)channel bottomsurfaces.

In embodiments of the first aspect of the present disclosure, performingthe protective treatment may comprise annealing 102, 1021 (FIG. 1), suchas for example annealing at a temperature in the range between 300° C.and 550° C. The annealing may be done in an inert atmosphere, such asfor example in nitrogen or argon, or in air. Annealing may be done underambient pressure or at a reduced pressure, such as in vacuum.

In embodiments of the first aspect of the present disclosure, performingthe protective treatment may comprise depositing 102, 1022 (FIG. 1) aprotective layer over the (nano)channel walls and over the (nano)channelbottoms. This is schematically illustrated in FIG. 4, showing aprotective layer 31 being provided on the (nano)channel walls 14 and onthe first insulating metal oxide barrier layer 21 that is present on the(nano)channel bottoms 15. The protective layer 31 is also formed on anupper surface of the porous layer 12.

In embodiments the protective layer may be a layer comprisinghydrophobic silane, e.g. formed by vapor deposition, for example in airor in vacuum, for example at a temperature in the range between 80° C.and 120° C. In other embodiments the protective layer may be a polymerlayer, e.g. formed by application of polymer solution onto the porewalls and bottoms of the template and drying. Such a protective polymerlayer may for example be formed by immersing the sample in 1% to 20%solution of polystyrene or PMMA (poly(methyl 2-methylpropanoate)) orPDMS (poly(dimethylsiloxane)), dissolved in acetone, in toluene or in achlorinated solvent such as dichloromethane and spin coating the excessof the solution, followed by drying at a temperature e.g. in the rangebetween 20° C. and 60° C., e.g. in air or in vacuum.

In embodiments of the first aspect of the present disclosure, performingthe protective treatment may comprise both depositing 102, 1022 (FIG. 1)a protective layer 31 over, e.g. directly on, the (nano)channel wallsand over the (nano)channel bottoms and annealing 102, 1021 (FIG. 1).

The protective treatment results in the formation of hydrophobicsurfaces on the (nano)channel walls and (nano)channel bottoms. Such ahydrophobic surface may provide protection against wetting, e.g. againstwetting by an etchant used in subsequent process steps, and therefore itmay provide protection against etching.

A method 100 according to embodiments of the first aspect of the presentdisclosure comprises, after the protective treatment 102, 1021, 1022, asecond anodization step 103 (FIG. 1). The second anodization step mayfor example be done using similar anodization conditions as used for thefirst anodization step, e.g. for a relatively short period, such as forexample 1 minute to 30 minutes. In embodiments of the first aspect ofthe present disclosure, this second anodization step affects the(nano)channel bottoms only and induces hydrophilic surfaces at the(nano)channel bottoms only. In embodiments wherein a protective layer 31has been deposited (FIG. 1, step 1022; FIG. 4), the second anodizationstep 103 results in removal of the protective layer 31 from the bottomof the plurality of spaced (nano)channels. The second anodization stepthus results in the formation of hydrophilic, unprotected (nano)channelbottoms (e.g. not protected against wetting). The second anodizationstep further results in removal of the first insulating metal oxidebarrier layer 21 from the (nano)channel bottoms. The second anodizationstep leaves the plurality of (nano)channel walls substantiallyunaffected, i.e. the plurality of (nano)channel walls remainsubstantially protected. The second anodization step results in furtheranodization only at the bottoms of the plurality of (nano)channels andcreates a second (unprotected) insulating metal oxide barrier layer atthe (nano)channel bottoms.

FIG. 5 schematically illustrates a cross section of the structure as maybe obtained after having performed the second anodization step in amethod according to an embodiment of the first aspect of the presentdisclosure wherein the protective treatment comprises annealing. More inparticular, FIG. 5 illustrates the first metal oxide barrier layer 21being removed from the channel bottoms 15 and being replaced by a secondmetal oxide barrier layer 22 at the channel bottoms 15 as a result ofthe second anodization step 103.

FIG. 6 schematically illustrates a cross section of the structure as maybe obtained after having performed the second anodization step in amethod according to an embodiment of the first aspect of the presentdisclosure wherein the protective treatment comprises depositing aprotective layer 31. More in particular, FIG. 6 illustrates theprotective layer 31 and the first metal oxide barrier layer 21 beingremoved from the channel bottoms 15 and being replaced by a second metaloxide barrier layer 22 at the channel bottoms 15 as a result of thesecond anodization step 103. FIG. 6 further illustrates that the channelwalls 14 remain protected by protective layer 31.

A method 100 according to embodiments of the first aspect of the presentdisclosure further comprises an etching step 104 (FIG. 1), for examplein an acidic etching solution or in a basic etching solution. At thisstage of the process the (nano)channel walls 14 are substantiallyprotected against etching, e.g. against wetting, as a result of theprotective treatment 102 previously performed, resulting in hydrophobicsurfaces at the (nano)channel walls. At this stage of the process onlythe (nano)channel bottoms 15 (more in particular the second insulatingmetal oxide barrier layer 22 at the (nano)channel bottoms 15) aresubject to wetting and thus etching. Therefore, this etching step 104only removes the second insulating metal oxide barrier layer 22 from theplurality of (nano)channel bottoms 15 and does not affect the porouslayer 12. As such, widening of the plurality of (nano)channels 13 duringthis etching step may be substantially avoided. The etching step may forexample comprise etching in an aqueous solution of H₃PO₄ or KOH. Theetching solution may comprise a surface tension adjusting agent such asfor example ethanol, isopropyl alcohol, acetone, or sodium dodecylsulfate, the present disclosure not being limited thereto. For example,a solution comprising 1 wt % to 30 wt % of H₃PO₄ and 1 wt % to 60 wt %of isopropyl alcohol in water may be used for the etching step.

FIG. 7 schematically illustrates a cross section of the structure as maybe obtained after having performed the etching step 104 in a method 100according to an embodiment of the first aspect of the present disclosurewherein the protective treatment comprises annealing. More inparticular, FIG. 7 illustrates that, after this etching step 104, the(nano)channel bottoms 15 are exposed (i.e. the second metal oxidebarrier layer 22 has been removed from the (nano)channel bottoms 15).The (nano)channel walls 14 remain unaffected, and there is no wideningof the (nano)channels 13.

FIG. 8 schematically illustrates a cross section of the structure as maybe obtained after having performed the etching step 104 in a method 100according to an embodiment of the first aspect of the present disclosurewherein the protective treatment comprises depositing a protectivelayer. More in particular, FIG. 8 illustrates that, after this etchingstep 104, the (nano)channel bottoms 15 are exposed (i.e. the secondmetal oxide barrier layer 22 has been removed from the (nano)channelbottoms 15). It also illustrates that the (nano)channel walls 14 arestill covered with the protective layer 31.

As illustrated in FIG. 7 and in FIG. 8, the structure obtained afterperforming the etching step comprises a template 20 comprising aplurality of spaced (nano)channels 13 aligned longitudinally along afirst direction (in the example shown the thickness direction Y of thevalve metal layer) and a substrate 10 supporting the template 20. FIG. 7and FIG. 8 thus illustrate examples of a template 20 according toembodiments of the second aspect of the present disclosure. In theexamples shown in FIG. 7 and FIG. 8 the substrate 10 corresponds to aremaining, non-anodized part of the valve metal layer 11.

After the etching step 104 the structure comprising the substrate 10 andthe template 20 (FIG. 7, FIG. 8) may be immersed in a basic solution ofzinc oxide to thereby produce a thin conductive zinc layer at the(nano)channel bottoms. The presence of such a thin conductive zinc layerat the (nano)channel bottoms enables or facilitates electroplating of avariety of metals in the plurality of (nano)channels in a subsequentstep.

In embodiments of the present disclosure the valve metal layer 11 mayconsist of a single layer or it may comprise more than one, e.g. aplurality of (stacked) layers, e.g. having a different composition. Forexample, the valve metal layer may consist of an aluminum layer, such asfor example an aluminum layer of 99% or higher purity, with a thicknessfor example in the range between 1 micrometer and 1 mm. In otherembodiments it may for example consist of a doped aluminum layer, suchas for example a copper doped aluminum layer, e.g. with a dopingconcentration in the range between 1% and 10% and a thickness e.g. inthe range between 1 micrometer and 1 mm. In other embodiments, it may bea layer stack comprising a first layer and a second layer, wherein thefirst layer is for example an aluminum layer of 99% or higher purity andwherein the second layer is for example a doped, e.g. copper doped,aluminum layer. The doped aluminum layer may for example have a dopingconcentration in the range between 1% and 10% and the thickness of thislayer may for example be in the range between 1 micrometer and 100micrometers.

In embodiments of the present disclosure the valve metal layer 11 may bea free-standing layer such as a free-standing foil, such as for examplean aluminum foil, e.g. having a thickness in the range between 10micrometers and 1 millimeter. In other embodiments of the presentdisclosure, the layer valve metal layer may be a non-free-standinglayer: it may for example be provided on a substrate, such as a flexiblesubstrate. Using a flexible substrate may allow for the fabrication offlexible solid-state batteries. Examples of flexible substrates that maybe used are a metal foil (such as aluminum, nickel or copper foil), micaand polyimide tape. The substrate may be coated with an electricallyconductive layer such as a nickel layer, a titanium layer, or a titaniumnitride layer.

In embodiments wherein the valve metal layer is a free-standing layer,the first anodization step may be done in part of the layer, i.e. notthroughout the valve metal layer, such that a part of the layer remainsunaffected. In such embodiments the remaining (non-anodized) part of thevalve metal layer can be maintained as a carrier (or substrate 10) forthe anodized part (template 20). In the further description, whenreference is made to a substrate, this may refer to a substrate on whicha valve metal layer is initially provided, or, in embodiments wherein afree-standing valve metal layer is used, it may refer to a substrate 10corresponding to a part of the valve metal layer that is remaining afterthe anodization step (i.e. the part that is not anodized, nottransformed into a porous layer), as for example illustrated in FIG. 7and FIG. 8. In embodiments wherein the anodization steps comprisecomplete immersion of a free standing valve metal layer 11 in ananodizing solution, resulting in the formation of a first porous layerof valve metal oxide at a first side of the valve metal layer andsimultaneously in the formation of a second porous layer of valve metaloxide at a second, opposite side of the valve metal layer, the substrate10 (non-anodized part) is present between the first porous layer and thesecond porous layer. In other words, a “first porouslayer/substrate/second porous layer” stack is formed.

The first anodization step of the valve metal layer, for example a layercomprising aluminum, may be performed by immersing the valve metal layeral in an anodizing solution, for example an acidic medium, such as asolution of sulfuric, oxalic, or phosphoric acid and applying a constantvoltage difference between the valve metal layer and a counter electrodesuch as a titanium electrode (e.g. a sheet or a mesh) or a platinumelectrode (potentiostatic anodization). The voltage difference may forexample be in the range between 10 V and 500 V. Alternatively, aconstant current may be applied to the valve metal layer through theanodizing solution (galvanostatic anodization). By selecting andcontrolling the anodization parameters the size of the plurality of(nano)channels (e.g. their diameter), and the distribution of theplurality of (nano)channels (e.g. the distance between neighboring(nano)channels) may be well controlled.

For example, experiments were performed wherein a potential of 40 V wasapplied between an aluminum layer (working electrode) and a counterelectrode, in a 0.3M oxalic acid at 30° C. to perform anodization of analuminum layer. This resulted in the formation of a plurality of 40 nmwide (i.e. having a diameter of 40 nm) spaced nanochannels having alongitudinal direction substantially orthogonal to the aluminum layersurface, the plurality of nanochannels being located at a distance fromeach other (distance between the centers of the nanochannels) of about100 nm in a direction substantially parallel with the aluminum layersurface.

The longitudinal size of the plurality of spaced nanochannels (i.e. thelength of the nanochannels, corresponding to the depth of anodizationinto the valve metal layer, i.e. the distance between the nanochannelbottoms and an upper surface of the valve metal layer) depends on theduration of the first anodization step. It may for example be in therange between 100 nm and 100 micrometers, the present disclosure notbeing limited thereto. The first anodization step may for example have aduration in the range between 1 hour and 12 hours.

Where the valve metal layer comprises an aluminum layer of high purity,such as for example an aluminum layer of 99% or higher purity, the firstanodization step results in the formation of a plurality of separated,non-interconnected (nano)channels. Where the valve metal layer comprisesa doped aluminum layer, such as for example a copper doped aluminumlayer, e.g. with a doping concentration in the range between 1% and 10%,the first anodization step results in the formation of a plurality ofspaced (nano)channels that are interconnected by interconnecting(nano)channels having a longitudinal orientation substantiallyorthogonal to the longitudinal orientation of the plurality of spaced(nano)channels. In embodiments wherein the valve metal layer is a layerstack comprising a first layer and a second layer, wherein the firstlayer is for example an aluminum layer of 99% or higher purity andwherein the second layer is a doped, e.g. copper doped, aluminum layer,a plurality of spaced (nano)channels is formed wherein the plurality ofspaced (nano)channels are separated (non-interconnected) in a firstregion (corresponding to the first layer) and wherein the plurality ofspaced (nano)channels are interconnected in a second region(corresponding to the second layer). The formation of interconnecting(nano)channels may result in an increased surface area and an improvedmechanical stability of (nano)structures that may be formed subsequentlywithin the template.

For example, experiments were performed wherein a potential of 40 V wasapplied between a Cu doped aluminum layer (working electrode) and acounter electrode, in a 0.3M oxalic acid at 30° C. This resulted in theformation of a plurality of 40 nm wide spaced nanochannels having alongitudinal direction substantially orthogonal to the metal layersurface, the plurality of spaced nanochannels being located at adistance from each other of about 100 nm in a direction substantiallyparallel with the metal layer surface, and in addition to the formationof 40 nm wide branches or interconnecting nanochannels having alongitudinal direction substantially parallel to the metal layer surfaceand being separated by a distance of about 100 nm in a directionsubstantially orthogonal to the metal layer surface.

In embodiments wherein the valve metal layer is provided on a substrate,such as a flexible substrate, coated with an electrically conductivelayer such as for example a nickel, titanium, or titanium nitride layer,the first anodization step may proceed till a plurality of(nano)channels if formed throughout the valve metal layer. In suchembodiments, the bottom of the plurality of (nano)channels thus formedis located at an interface between the valve metal layer and theunderlying electrically conductive layer, i.e. at an interface betweenthe porous layer resulting from the first anodization step and thesubstrate 10. When during the first anodization step the bottom of theplurality of (nano)channels reaches the underlying substrate 10, thisleads to a decrease of current in case of potentiostatic anodization, oran increase in potential in case of galvanostatic anodization. In thisway, it may be easily detected when the spaced (nano)channels 13 thusformed reach the substrate 10, i.e. at which moment the plurality ofspaced (nano)channels are formed throughout the valve metal layer.

In embodiments, the second anodization step 103 may be performed underirradiation of ultrasonic waves. Such ultrasonic waves may for examplebe generated by an ultrasound generating horn, immersed in the anodizingsolution. Providing ultrasonic waves may facilitate removal of the firstinsulating metal oxide barrier layer 21 and, if present, removal of theprotective layer 31 from the (nano)channel bottoms during the secondanodization step 103. Providing ultrasonic waves may further facilitateremoval of the second insulating metal oxide barrier layer 22 from the(nano)channel bottoms during the etching step 104.

According to a third aspect, the present disclosure is related to amethod for forming a plurality of spaced (nano)structures, such as forexample a plurality of spaced electrically conductive (nano)structures,on a substrate. An example of a method according to the third aspect ofthe present disclosure is schematically illustrated in FIG. 9, showing aflow chart comprising an example process sequence, and in FIG. 7, FIG.8, FIG. 10, and FIG. 11, schematically showing cross sectionsillustrating results of successive steps of the process sequence of FIG.9.

As illustrated in the example shown in FIG. 9, a method 200 according toan embodiment of the third aspect of the present disclosure comprisesfirst transforming 201 at least part of a valve metal layer 11 into atemplate 20 comprising a plurality of spaced (nano)channels 13 alignedlongitudinally along a first direction, in accordance with a method 100of the first aspect of the present disclosure. Examples of a structureresulting from this step 201 are schematically shown in FIG. 7 and FIG.8.

The method 200 further comprises depositing 202 a solid functionalmaterial within the (nano)channels 13 of the template 20. This resultsin formation of a plurality of spaced (nano)structures 40 inside theplurality of spaced channels 13, the plurality of spaced(nano)structures being aligned longitudinally along the first direction,as schematically shown in FIG. 10. In the example shown in FIG. 10, theplurality of (nano)channels 13 is completely filled with the solidfunctional material, resulting in a plurality of (nano)wires 40 having alength (size in their longitudinal direction Y) substantially equal to athickness of the template 20. However, the present disclosure is notlimited thereto and in embodiments of the second aspect of the presentdisclosure the plurality of (nano)channels 13 may be filled onlypartially. For example, in embodiments the functional material may bedeposited within the plurality of (nano)channels 13 only in part oflongitudinal direction Y, resulting in a plurality of (nano)structures40 having a length smaller than a thickness of template 20. This can becontrolled by controlling the deposition time.

In embodiments of a method of the third aspect of the present disclosurethe solid functional material may be deposited within the plurality of(nano)channels 13 to thereby fully fill the plurality of (nano)channels13 in lateral direction X, which may result for example in the formationof a plurality of (nano)wires or (nano)pillars within the plurality of(nano)channels. In other embodiments, the solid functional material maybe deposited within the plurality of (nano)channels 13 to thereby onlypartially fill the plurality of (nano)channels 13 in lateral directionX, which may for example result in the formation of a plurality of(nano)tubes or hollow (nano)wires inside the plurality of (nano)channels13.

After having deposited the solid functional material, the template 20may be removed by etching 203 (FIG. 9). For this etching step 203, forexample a solution comprising 0.1M to 1M KOH may be used. The etchingtime may for example be in the range between 20 minutes and 90 minutes,and etching may be done at a temperature e.g. in the range between 20°C. and 60° C. The resulting structure is schematically shown in FIG. 11.It contains a plurality of spaced (nano)structures 40 on a substrate 10,more in particular on an electrically conductive substrate 10. Thediameter of the plurality of (nano)structures 40, i.e. their size inlateral direction X, and their separation (i.e. the center-to-centerdistance between neighboring (nano)structures 40) depends on thediameter and separation of the (nano)channels 13 of the template 20. Thediameter of the plurality of (nano)wires may for example be in the rangebetween 10 nm and 500 nm, for example between 10 nm and 300 nm, e.g.between 15 nm and 200 nm or between 50 nm and 200 nm, and theirseparation distance may for example be in the range between 15 nm and500 nm, e.g. between 50 nm and 250 nm, the present disclosure not beinglimited thereto.

In embodiments wherein the template is formed by anodization of only apart of the valve metal layer 11 (i.e. wherein anodization is done onlypartially in the thickness direction Y of the valve metal layer 11),such as in embodiments using a free-standing valve metal layer, thenon-anodized part of the valve metal layer remains as a carrier orsubstrate 10 for the plurality of spaced (nano)structures 40 formedwithin the template. In such embodiments removal of the template 20results in a plurality of spaced (nano)structures 40 on a remaining partof the valve metal layer (herein also referred to as a substrate 10),wherein the plurality of spaced (nano)structures 40 is substantiallyaligned longitudinally with their longitudinal direction along the firstdirection, such as for example a direction Y substantially orthogonal tothe valve metal layer (substrate) surface, i.e. substantially orthogonalto direction X.

In embodiments of the third aspect of the present disclosure, depositingthe solid functional material may comprise depositing an electricallyconductive material, a semiconductor material, an electricallyinsulating material or a combination thereof. Depositing the solidfunctional material may for example comprise Chemical Vapor Deposition,e.g. Atomic Layer Deposition, the present disclosure not being limitedthereto. Depositing an electrically conductive material may for examplecomprise depositing the material by galvanostatic or potentiostaticelectrodeposition or plating, the present disclosure not being limitedthereto.

For example, in a method 200 according to embodiments of the thirdaspect of the present disclosure, nickel (nano)structures 40 may begrown galvanostatically from a solution of nickel sulphamate and boricacid and/or nickel chloride at a temperature in the range between 20° C.and 60° C. The growth may be performed by application of a cathodiccurrent e.g. (1-20 mA/cm²) between the electrically conductive substrate10 (or an electrically conductive layer being part of the substrate 10)and a metallic counter electrode, such as a nickel or platinum counterelectrode. The (nano)structures are formed inside the plurality ofspaced (nano)channels of the template and may form longitudinallyaligned spaced (nano)wires or (nano)pillars or a three-dimensionalnetwork comprising longitudinally aligned spaced (nano)wires andinterconnecting (nano)structures between the spaced (nano)wires,depending on the architecture of the (nano)channels of the template. Thelength of the (nano)wires can be controlled by controlling the time ofdeposition. For instance, it was experimentally found that deposition ofnickel at 10 mA/cm² for 150 s inside the channels of a porous templateformed from copper doped aluminum leads to the formation of 2micrometers high interconnected nickel (nano)wires.

For example, in a method 200 according to embodiments of the thirdaspect of the present disclosure, a catalyst material such as forexample gold may first be provided at the plurality of (nano)channelbottoms of the template, e.g. by plating, and afterwards a semiconductorfunctional material, such as for example Si, Ge, InP, GaP, or GaAs maybe deposited within the (nano)channels, e.g. by Chemical VaporDeposition, to thereby form a plurality of semiconducting (nano)wiresinside the plurality of (nano)channels.

For example, in a method 200 according to embodiments of the thirdaspect of the present disclosure, a Metal-Insulator-Metal stack may bedeposited within the plurality of (nano)channels, for example by AtomicLayer Deposition. In such embodiments the insulator material may forexample comprise alumina or HfO₂, and the metal layer may for examplecomprise TiN or Ru, the present disclosure not being limited thereto.

Although in some embodiments of the third aspect of the presentdisclosure the plurality of (nano)structures are aligned longitudinallywith their longitudinal direction Y substantially orthogonal to thevalve metal layer (substrate) surface, i.e. substantially orthogonal todirection X, the present disclosure is not limited thereto. Inembodiments of the present disclosure the longitudinal direction of theplurality of spaced (nano)structure may make an angle of from forexample 60° to 90° with the substrate surface on which the (nano)wiresabut. In some embodiments, this angle is from 80° to 90°, e.g.substantially 90°, i.e. substantially orthogonal.

According to a fourth aspect, the present disclosure related to anentity comprising a substrate and a plurality of spaced structures onthe substrate, the plurality of spaced structures being alignedlongitudinally along a first direction, as may be obtained using amethod according to an embodiment of the third aspect of the presentdisclosure. FIG. 11, FIG. 12A, and FIG. 12B each schematically show across section of an example of an entity according to an embodiment ofthe fourth aspect of the present disclosure. FIG. 12A illustrates anexample of an entity 50 comprising a substrate 10 and a plurality ofspaced structures 51 being aligned longitudinally along a firstdirection forming an angle of about 90° with respect to a surface of thesubstrate 10, i.e. being oriented substantially orthogonal to a surfaceof the substrate. FIG. 12B illustrates an example of an entity 50comprising a substrate 10 and a plurality of spaced structures 51 beingaligned longitudinally along a first direction forming an angle of about90° with respect to a surface of the substrate 10, and furthercomprising a plurality of interconnecting structures 52 oriented along asecond direction substantially orthogonal to the first direction.

According to a fifth aspect, the present disclosure relates to a devicecomprising an entity according to an embodiment of the fourth aspect ofthe present disclosure. Examples of devices wherein such an entity maybe used are batteries, fuels cells, sensors, supercapacitors (such asMetal-Insulator-Metal supercapacitors), electrolyzers,photo-electrolyzers, and chemical reactors.

According to a sixth aspect, the present disclosure relates to a methodfor forming a layer of functional material on an electrically conductivesubstrate. A method according to an embodiment of the sixth aspect ofthe present disclosure may for example be used for depositing an activeelectrode material on, for example, a transition metal substrate. Anexample of a method 300 according to the sixth aspect of the presentdisclosure is schematically illustrated in FIG. 13, showing a flow chartcomprising an example process sequence, and in FIG. 14 to FIG. 16,schematically showing cross sections illustrating results of successivesteps of the process sequence of FIG. 13.

As illustrated in the example shown in FIG. 13, a method 300 accordingto an embodiment of the sixth aspect of the present disclosure comprisesdepositing 301 an interlayer on an electrically conductive substrate.The interlayer may for example have a thickness in the range between 0.5nm and 30 nm, for example in the range between 0.5 nm and 5 nm, e.g. inthe range between 0.5 nm and 3 nm.

In embodiments of the sixth aspect of the present disclosure thematerial of the interlayer is selected to provide protection againstthermal degradation such as for example oxidation (i.e. to preventoxidation) of the underlying electrically conductive substrate materialduring further process steps. For example, the material of theinterlayer may be selected to have a low diffusivity of oxygen. It maybe selected to be chemically inert with respect to a functional materialprecursor plating bath, to thereby prevent electro-oxidation of theunderlying substrate material, e.g. transition metal, duringelectrodeposition. It may be selected to be chemically inert withrespect to a layer of functional material precursor being depositedthereon in a further process step and/or being annealed in a furtherprocess step, to thereby prevent thermal oxidation of the underlyingmetal. In the context of the present disclosure, a low diffusivity ofoxygen may refer to an oxygen diffusivity lower than the oxygendiffusivity in NiO at temperatures in the range between 300° C. and 500°C. In embodiments of the sixth aspect of the present disclosure thefunctional material precursor layer may for example be an electrodematerial precursor layer and the layer of functional material formed onthe electrically conductive substrate may for example be an activeelectrode material, such as e.g. an active cathode material or an activeanode material of a solid-state battery cell or battery.

In embodiments according to the sixth aspect of the present disclosuredifferent interlayers may be combined, i.e. a stack of different typesof interlayers may be deposited, to thereby provide protection of thesubstrate against both thermal oxidation and electro-oxidation.

The interlayer may for example comprise a transition metal oxide, anoble metal or a noble-metal oxide. For example, the interlayer maycomprise NiO_(x), Cr₂O₃, TiO₂, RuO, RuO₂, Ru, Au, or Pt, the presentdisclosure not being limited thereto. For example, a transition metaloxide interlayer such as a nickel oxide interlayer or a chromium oxideinterlayer may be deposited using an electrodeposition process, e.g. ina weakly basic or basic solution having a pH in the range of 7 to 12.For example, the interlayer 31 may be deposited by immersing thesubstrate in a 0.1 M-1M solution of sodium citrate and applying aconstant anodic current, for example in the range between 1 mA/cm² and100 mA/cm² between the substrate (e.g. comprising a plurality of nickel(nano)wires) and a metallic counter electrode, for example for 1 to 10minutes.

In particular, in embodiments wherein the electrically conductivesubstrate is a transition metal substrate the interlayer maysubstantially prevent or reduce oxidation of the transition metal duringfurther process steps (e.g. for fabricating a battery cell). Forexample, it may prevent dissolution of nickel (nano)structures duringdeposition of a MnO_(x) cathode precursor material layer, for example byanodic electrodeposition, and/or it may improve the resistance of nickel(nano)structures against oxidation during later thermal treatments, suchas for example annealing for activating the layer of cathode precursormaterial.

A method according to embodiments of the sixth aspect of the presentdisclosure may be used for conformally forming a layer of active cathodematerial on a structure comprising a plurality of spaced(nano)structures, e.g. on a plurality of spaced (nano)wires or aplurality of spaced (nano)tubes, e.g. as may be formed in accordancewith a method 200 of the third aspect of the present disclosure, forexample on a plurality of spaced (nano)structures formed of anelectrically conductive transition metal. Some examples of such astructure (three-dimensional substrate) are schematically illustrated inFIG. 11, FIG. 12A, and FIG. 12B, but the present disclosure is notlimited thereto.

When referring to a substrate in the context of the sixth aspect of thepresent disclosure, an electrically conductive substrate is indicated.This includes at one hand substrates or structures entirely made of anelectrically conductive material, and at the other hand also substratesor structures comprising different materials or different materiallayers, with an electrically conductive layer, such as for example anickel layer, being exposed at a surface thereof. An example of anelectrically conductive substrate, more in particular athree-dimensional electrically conductive substrate on which layer ofactive cathode material may be formed in a sixth aspect of the presentdisclosure is schematically illustrated in FIG. 11, FIG. 12A, and FIG.12B.

FIG. 14 schematically shows an electrically conductive substrate 60,after deposition 301 of an interlayer 41 according to a method of thesixth aspect of the present disclosure.

In a next step, after deposition of the interlayer 41, a method 300according to the sixth aspect of the present disclosure comprisesdepositing 302 (FIG. 13) a functional material precursor layer on theinterlayer 41. The functional material precursor layer may for examplebe conformally deposited by potentiostatic or galvanicelectrodeposition, such as anodic electrodeposition. FIG. 15 illustratesthe structure after conformal deposition 302 of a functional materialprecursor layer 42 on the interlayer 41. A conformally deposited layeris a layer with a uniform thickness, exactly following the topography ofthe underlying layer.

In a subsequent step, a method 300 according to the sixth aspect of thepresent disclosure comprises activating 302 (FIG. 13) the functionalmaterial precursor layer 42 by annealing, to thereby form the layer offunctional material 43. The resulting structure is schematicallyillustrated in FIG. 16, showing the electrically conductive substrate60, in the example comprising a plurality of electrically conductive(nano)structures 61, being conformally coated with a layer of functionalmaterial 43, the layer of functional material 43 being provided over theinterlayer 41.

The functional material precursor layer 42 may for example be a layer ofcathode precursor material, for example comprising manganese oxide,manganese dioxide, cobalt oxide, manganese nickel oxide, iron phosphate.The layer of functional material 43 may for example be a layer of activecathode material, for example comprising lithium manganese oxide,lithium cobalt oxide, lithium iron phosphate, or lithium sulphide, thepresent disclosure not being limited thereto.

For example, depositing 302 a layer of cathode precursor material 42 onthe interlayer 41 may comprise depositing a manganese dioxide (MnO₂)layer on the interlayer by applying a constant anodic current (e.g. inthe range between 1 mA/cm² and 100 mA/cm²) between the electricallyconductive substrate and a metallic counter electrode, after immersingthe substrate with the interlayer in a solution containing for example0.1M to 10M MnSO₄, e.g. 0.1M to 1M MnSO₄, and 0.1M to 10M H₂SO₄, 0.1M to1M H₂SO₄, at a temperature in the range between 20° C. and 100° C., e.g.between 20° C. and 50° C. The thickness of the layer of cathodeprecursor material may be controlled by controlling the time ofelectrodeposition. A layer of MnO_(x) material deposited as describedhereinabove typically has a porosity in the range between 10% and 80%.Such a porosity may allow for the accommodation of an ion precursor foractivating the layer of cathode precursor material (MnO_(x)), such asfor example a lithium containing precursor for conversion into lithiatedmanganese oxide. The porosity may allow for the accommodation of anelectrolyte, which may be provided in a further process step.

Activating 302 the layer of cathode precursor material by annealingcomprises activating the layer of cathode precursor material for ioninsertion/extraction. This annealing may be done in the presence of anion containing precursor, such as for example a lithium containingprecursor, a sodium containing precursor or a magnesium containingprecursor, to thereby form a layer of active cathode material. Thisactivating step may for example comprise coating the layer of cathodeprecursor material with a lithium-containing precursor such as alithium-containing salt and afterwards annealing, for example annealingat a temperature in the range between 250° C. and 600° C.

Examples are provided hereinbelow, which illustrate experiments in whicha method according to embodiments of the sixth aspect of the presentdisclosure was used for forming a layer of active cathode material on anelectrically conductive transition metal substrate. These examples areprovided for illustrating features of embodiments of the third aspect ofthe present disclosure, and to aid the skilled person in reducing thedisclosure to practice. However, these examples should not be construedas limiting the disclosure in any way.

The formation of the NiO containing interlayer was found to show aself-terminating behavior. The thickness of this interlayer was found tobe limited to about 1 nm.

It was experimentally shown that the interlayer 41 may preventelectro-oxidation of the underlying nickel substrate 40 duringsubsequent MnO_(x) electroplating, while the deposition of MnO_(x) byelectroplating is still possible.

This is illustrated in FIG. 17, showing potential transients as measuredduring galvanostatic deposition of a MnO_(x) cathode precursor layer onNi nano-mesh samples. The samples used in the experiments comprise a 3.3micrometer thick Ni nano-mesh layer on a TiN/Si wafer. For a first part(1) of the samples, an interlayer 41 was provided on the Ni nano-meshlayer, by electrodeposition in a 0.4M sodium citrate solution at 30° C.and by subsequent application of an anodic current at 2.4 mA/cm² and 6mA/cm² current density for 60 s each. A Pt counter electrode was used.For a second part (2) of the samples no interlayer was provided, leavingthe Ni nano-mesh layer exposed. The galvanostatic deposition of MnO_(x)was done in a 0.3M MnSO₄+0.55M H₂SO₄ bath at 30° C. using a currentdensity of 16 mA/cm² footprint (or 0.16 mA/cm² of nano-mesh real area).The Ni nano-mesh layer acted as a working electrode, a platinum mesh wasused as a counter electrode and Ag/AgCl as a reference electrode.

The curve labeled (b) in FIG. 17 shows potential transients as measuredon the Ni nano-mesh substrate covered with an interlayer 41, accordingto an embodiment of the third aspect of the present disclosure. Thecurve corresponds to the MnO_(x) potential and illustrates MnO_(x)deposition on the Ni nano-mesh substrate. A SEM analysis did not showany visible degradation of the nano-mesh. The curve labeled (a) in FIG.17 shows potential transients as measured on the Ni nano-mesh substrateon which no interlayer was provided and wherein the Ni was thus exposedto the electroplating solution. It corresponds to the potential of Nidissolution. A SEM analysis showed degradation of the Ni nano-mesh, anddid not reveal any MnO_(x) deposition.

This is further illustrated in FIG. 18, showing results of cyclicvoltammetry experiments. In these experiments, samples comprising aplanar 150 nm thick Ni layer provided by Physical Vapor Deposition ontop of a 150 nm thick TiN layer on a Si wafer were used. The samplelabeled (a) in FIG. 18 was cleaned with acetone and IPA and dried withN₂, while the sample labeled (b) was cleaned with 20% HCl, water and IPAand dried with N₂. An interlayer was subsequently provided on sample (b)by electrochemical deposition. An anodic current of 6 mA/cm² was passedthrough the nickel layer immersed in a sodium citrate bath at 30° C.,for 180 s. It was found that this resulted in a very thin layer ofNiO/Ni(OH)₂, possibly functionalized with citrate moieties, formed onthe surface of nickel layer: Ni+3H₂O→NiO+2e⁻+2H₃O⁺. For theelectrodeposition of a MnO_(x) layer the samples were used as a workingelectrode, a platinum mesh was used as a counter electrode and Ag/AgCl(3M KCL) was used as a reference electrode. The solution consisted of0.3M MnSO₄ and 0.55M H₂SO₄. The cyclic voltammograms shown in FIG. 18were recorded between the open circuit potential of the workingelectrode and 1.5 V vs Ag/AgCl, at a scanning speed of 10 mV/s, at 25°C. Curves labeled (a) correspond to a structure without an interlayerbeing provided before deposition of the MnO_(x) layer, whereas curveslabeled (b) correspond to a structure having an interlayer providedthereon before deposition of the MnO_(x) layer, in accordance with anembodiment of the third aspect of the present disclosure. Uponapplication of anodic potentials, nickel dissolution peaks between −0.1Vand 0.3V can clearly be seen for sample (a) without an interlayer beingprovided on the nickel electrode, and no nickel dissolution is visiblefor sample (b) having a NiO interlayer between the nickel electrode andthe MnO_(x) active cathode material. No MnO_(x) deposition was observedfor sample (a). This illustrates that the anodic dissolution of nickelin the acidic medium is more thermodynamically and kinetically favorablethan deposition of MnO_(x).

In embodiments of a method according to the sixth aspect of the presentdisclosure, the interlayer 41 may further protect the underlying metal,e.g. nickel, for oxidation during later annealing steps. For example,the step of activating 303 the layer of cathode precursor material 42may comprise lithiation (activation for lithium insertion/extraction),resulting in conversion of the cathode precursor material (e.g. MnO_(x))to a lithium-containing active cathode material (e.g. manganese oxide(LMO)). The lithiation may comprise an electrochemical conversion or asolid-state conversion. The lithiation step may for example comprisecoating the MnO_(x) layer with a lithium-containing salt (e.g. Li₂CO₃,LiOH, LiNO₃) and annealing at an elevated temperature, for example at atemperature in the range between 250° C. and 600° C., to formelectroactive lithium manganese oxide. It was experimentally found that,due to the oxidizing nature of MnO_(x), upon annealing in a nitrogenatmosphere of a sample comprising a MnO_(x) layer being provideddirectly on a substrate comprising nickel nanowires, the nickelnanowires were oxidized. A relatively thick nickel oxide layer wasformed (e.g. 5 nm to 20 nm thick, corresponding to 25% to 100% of thenanowires diameter). The reaction can be written as follows:

yNi+2MnO_(x) →yNiO+MnO_((x-0.5y))

where 1<x≤2 and y≤−2(1-x).

In most extreme cases (longer annealing times or higher temperatures),complete oxidation of nickel (nano)wires was observed. Nickel oxide is ap-type semiconductor and thus is not suitable as a material for abattery current collector, which should be conductive for both negativeand positive currents.

By providing an interlayer 41 according to embodiments of the sixthaspect of the present disclosure, such oxidation of the currentcollector material (such as nickel) may be substantially avoided.Embodiments according to the sixth aspect of the present disclosure mayinclude an interlayer that forms an effective oxygen diffusion barrierwhich shields the underlying metal, e.g. nickel, from oxidation, e.g. bythe active cathode material precursors, e.g. MnO_(x) precursors. Theinterlayer may be a thin layer, e.g. having at thickness smaller than 30nm, e.g. smaller than 5 nm, in view of not adding excessive volume tothe electrode and to have reasonable electronic conductance.

The interlayer can for example consist of nickel oxide as describedabove, or it can consist of a transition metal such as titanium orchromium, or a noble metal such as ruthenium, gold, or platinum. Theinterlayer may also be formed with oxides of such metals. The metal ormetal oxide interlayers may be coated on (nano) structures, e.g. nickel(nano)structures, either by electrodeposition or by gas phase methodssuch as ALD (Atomic Layer Deposition) or CVD (Chemical VaporDeposition). The interlayer can in general be deposited by variousmethods, such as but not limited to, electrodeposition, physical vapordeposition, chemical vapor deposition, or atomic layer deposition.Atomic layer deposition may yield the highest conformality of thedeposited interlayer on high aspect ratio surfaces and may thus for thatreason be used. After coating, an additional step of annealing in areducing atmosphere (e.g. H₂/Ar, forming gas) may optionally be done toreduce the metal oxide to its corresponding metallic form.

In an embodiment, a spinel LiMn₂O₄ layer of active cathode material maybe formed. After deposition of a layer of MnO_(x) as described above,the substrate with deposited MnO_(x) may be immersed in a solutioncontaining lithium salts such as 0.1M to 3M LiOH or LiNO₃ or Li₂CO₃, andsubjected to spin coating for removal of excess solution. Next anannealing step, e.g. at 350° C., may be done to form spinel phaseLiMn₂O₄. The excess of lithium salt may be further removed by washing inwater. The so-formed active material typically has a porosity between10% and 80% and may allow accommodating a volume of later providedelectrolyte material.

According to a seventh aspect, the present disclosure relates to amethod for fabricating a solid-state battery cell, wherein the methodcomprises forming a plurality of electrically conductive(nano)structures according to an embodiment of the third aspect of thepresent disclosure, and forming a first layer of active electrodematerial on the plurality of electrically conductive structures, whereinthe first layer of active electrode material conformally coats surfacesof the plurality of electrically conductive structures. Next a solidelectrolyte layer is deposited over the layer of active electrodematerial, and a second layer of active anode material is formed over thesolid electrolyte layer. One of the first layer of active electrodematerial and the second layer of active electrode material forms acathode layer and the other one forms an anode layer of the solid-statebattery cell. A current collector layer may be deposited over the secondlayer of active electrode material.

In embodiments according to the seventh aspect of the present disclosurethe substrate comprises an electrically conductive layer. In embodimentsthe substrate may consist of an electrically conductive layer, such asfor example a metal foil, e.g. an aluminum, copper, chromium, or nickelfoil. The plurality of spaced electrically conductive (nano)structuresmay for example comprise (nano)wires or (nano)tubes. The plurality ofspaced electrically conductive (nano)structures may for example comprisenickel, aluminum, copper, or chromium and they may have a longitudinaldirection oriented substantially orthogonal to the substrate surface.The cathode material may for example contain manganese (di)oxide (e.g.MnO or MnO₂), lithium manganese oxide (e.g. LiMn₂O₄, LiMnO₂, orLi₂MnO₃), lithium manganese nickel oxide, lithium cobalt oxide (e.g.LiCoO₂ or LiCo₂O₄), lithium nickel oxide (e.g. LiNiO₂), cobalt (II,III)oxide, lithium manganese phosphate (e.g. LiMnPO₄), lithium ironphosphate (e.g. LiFePO₄), lithium cobalt phosphate (e.g. LiCoPO₄),lithium sulfide (e.g. Li₂S), lithium titanium sulfide (e.g. LiTiS₂),sodium iron phosphate, tungsten selenide, vanadium pentoxide, molybdenumdisulfide, or sulfur. The layer of active anode material may for examplecomprise lithium titanium oxide (e.g. Li₄Ti₅O₁₂), metallic lithium,titanium dioxide, vanadium pentoxide, silicon, graphite, manganese(II)monoxide, metallic magnesium, metallic sodium, metallic potassium,metallic germanium or metallic tin. In some embodiments, it may beformed by a method according to an embodiment of the third aspect of thepresent disclosure. The current collector layer may for example comprisemetallic lithium or a foil of nickel, aluminum, copper, chromium, orzinc, the present disclosure not being limited thereto.

In embodiments according to the seventh aspect of the presentdisclosure, a solid electrolyte layer is deposited over the first layerof active electrode material. The solid electrolyte layer may bedeposited conformally over the first layer of active electrode materialor it may be deposited non-conformally, such as for example with anupper surface that is substantially flat and substantially parallel tothe substrate surface. In embodiments, a combination of a conformallycoated solid electrolyte layer and a non-conformally coated solidelectrolyte layer may be used. For example, a first solid electrolytelayer may be conformally deposited over the first layer of activeelectrode material and next a second solid electrolyte layer may benon-conformally deposited over the first solid electrolyte layer.Deposition of a solid electrolyte layer may for example be done usingelectrodeposition, by drop casting an electrolyte precursor solution andspin coating the excess of the precursor solution, or by vapor phasedeposition such as atomic layer deposition.

For example, in an embodiment the solid electrolyte layer may compriselithium phosphorous oxynitride (LiPON) or a solid composite electrolyte(e.g. Li₂S—P₂S₅). A solid LiPON electrolyte layer may for example bedeposited by ALD cycling of lithium tert-butoxide, trimethylphosphateand water, with or without addition of nitrogen in the depositionchamber. This leads to impregnation of the cathode active material withthe solid-state electrolyte. Additionally, a solid electrolyte layer,for example having a thickness in the range between 50 nm and 1micrometer may be deposited on top of the stack, e.g. by sputter coatingor spin coating. Following the additional deposition, the stack may besubjected to a heat treatment, for example at a temperature in the rangebetween 50° C. and 350° C., for enhanced gelification or sinteringpurposes.

In embodiments according to the seventh aspect of the presentdisclosure, a second layer of active electrode material is formed overthe solid electrolyte layer. The second layer of active electrodematerial may be deposited conformally over the solid electrolyte layeror it may be deposited non-conformally, such as for example with anupper surface that is substantially flat and substantially parallel tothe substrate surface. In embodiments, a combination of a conformallycoated second layer of active electrode material and a non-conformallycoated layer may be used. Deposition of a second layer of activeelectrode material may for example be done using vapor phase deposition,such as DC sputtering, thermal evaporation, atomic layer deposition orchemical vapor deposition. For example, in an embodiment, the secondactive electrode material may be metallic lithium. The layer of metalliclithium may for example have a thickness in the range between 0.5micrometer and 10 micrometers. It may for example be deposited bythermal evaporation of lithium onto the solid electrolyte layer. Inanother embodiment, the second layer of active electrode material mayfor example comprise spinel Li₄Ti₅O₁₂ or amorphous TiO₂. These activeanode materials may for example be deposited by DC sputtering or ALDcoating, followed by annealing (sintering), e.g. at a temperature in therange between 200° C. and 400° C. If some embodiments a thinelectrically conductive layer, such as an aluminum layer or a nickellayer, e.g. having a thickness in the range between 50 nm and 1micrometer, may be deposited on top of the layer of active anodematerial, for example by DC sputtering or thermal evaporation.

The battery cell thus obtained may be coated with a polymer layer suchas a polydimethoxysilane (PDMS) layer or a poly(methyl methacrylate)layer, for example with a thickness in the range between 100 nm and 5micrometer, to protect it from air and moisture. The polymer layer mayfor example be applied by spin coating, blade coating, or drop casting,followed by curing at a temperature for example in the range between 20°C. and 150° C.

According to an eighth aspect, the present disclosure is related to amethod for fabricating a solid-state battery cell, the methodcomprising: forming a plurality of spaced electrically conductivestructures on a substrate; forming a first layer of active electrodematerial on the plurality of spaced electrically conductive structuresaccording to a method of the sixth aspect of the present disclosure,wherein the first layer of active electrode material conformally coatssurfaces of the plurality of electrically conductive structures;depositing a solid electrolyte layer over the first layer of activeelectrode material; and depositing a second layer of active electrodematerial over the solid electrolyte layer. One of the first layer ofactive electrode material and the second layer of active electrodematerial forms a cathode layer and the other one forms an anode layer ofthe solid-state battery cell. A current collector layer may be depositedover the second layer of active electrode material.

According to a ninth aspect, the present disclosure is related to amethod for fabricating a solid-state battery. A method according to theninth aspect of the present disclosure comprises: fabricating aplurality of solid-state battery cells in accordance with an embodimentof the seventh or the eighth aspect of the present disclosure; andforming a stack of the plurality of solid-state battery cells with asolid electrolyte being provided in between neighboring solid-statebattery cells.

According to a tenth aspect, the present disclosure is related to asolid-state battery cell. An example of a solid-state battery cellaccording to an embodiment of the tenth aspect of the present disclosureis schematically illustrated in FIG. 19. In the example shown, thesolid-state battery cell 80 comprises a plurality of spaced electricallyconductive structures 70. More in particular, FIG. 19 shows anembodiment wherein the plurality of spaced electrically conductivestructures 70 is aligned along a direction substantially orthogonal to asubstrate 10 on which those structures are provided. This is only anexample, and in embodiments of the tenth aspect of the presentdisclosure other orientations, shapes, and/or configurations may beused. As illustrated in FIG. 19, the plurality of spaced electricallyconductive structures 70 is conformally coated with an interlayer 71,the interlayer 71 being conformally coated with a first layer of activeelectrode material 72. The solid-state battery cell 80 further comprisesa solid electrolyte layer 73 over the first layer of active electrodematerial 72. In the example shown, the solid electrolyte layer 73 isprovided non-conformally and has an upper surface that is substantiallyflat and substantially parallel to a surface of the substrate 10.However, this is only an example and the present disclosure is notlimited thereto. The solid-state battery cell 80 further comprises asecond layer of active electrode material 74 over the solid electrolytelayer 73.

In a solid-state battery cell 80 according to an embodiment of the tenthaspect of the present disclosure the interlayer 71 may for examplecomprise a transition metal oxide layer, a noble metal layer, or anoble-metal oxide layer. It may for example have a thickness in therange between 0.5 nm and 30 nm. One of the first layer of activeelectrode material 72 and the second layer of active electrode material74 forms a cathode layer and the other one forms an anode layer of thesolid-state battery cell 80.

Battery cells of the tenth aspect of the present disclosure may furtherbe stacked into batteries or battery packs, for example for increasingthe delivered electrical potential or current of the device upondischarging.

According to an eleventh aspect, the present disclosure relates to asolid-state battery comprising at least one solid-state battery cell inaccordance with an embodiment of the tenth aspect of the presentdisclosure. FIG. 20 schematically shows a cross section of an example ofsuch a solid-state battery 90. In the example shown in FIG. 20, thesolid-state battery 90 comprises a single solid-state battery cell 80corresponding to the example illustrated in FIG. 19. However, thepresent disclosure is not limited thereto. Further, a solid-statebattery 90 in accordance with the eleventh aspect of the presentdisclosure may comprise more than one, for example two, for example aplurality of solid-state battery cells 80 (not illustrated).

In the solid-state battery shown in FIG. 20, the plurality ofelectrically conductive structures 70 have the function of a firstcurrent collector of the battery 90. The solid-state battery 90 furthercomprises a second current collector 75 over the second layer of activeelectrode material 74, and an encapsulation layer 76.

The foregoing description details certain embodiments of the disclosure.It will be appreciated, however, that no matter how detailed theforegoing appears in text, the disclosure may be practiced in many ways.It should be noted that the use of particular terminology whendescribing certain features or aspects of the disclosure should not betaken to imply that the terminology is being re-defined herein to berestricted to including any specific characteristics of the features oraspects of the disclosure with which that terminology is associated.

It is to be understood that although example embodiments, specificconstructions and configurations, as well as materials, have beendiscussed herein for methods and devices according to the presentdisclosure various changes or modifications in form and detail may bemade without departing from the scope of this disclosure. For example,steps may be added or deleted to methods described within the scope ofthe present disclosure.

Whereas the above detailed description as well as the summary of thedisclosure has been focused on a method for fabricating a device, thepresent disclosure also relates to a device comprising patterned layersobtained using a method according to any of the embodiments as describedabove.

1. A method for transforming at least part of a valve metal layer into atemplate comprising a plurality of spaced channels alignedlongitudinally along a first direction, the method comprising: a firstanodization step comprising anodizing at least part of the valve metallayer in a thickness direction to form a porous layer of valve metaloxide comprising a plurality of channels, wherein each channel haschannel walls aligned longitudinally along the first direction and has achannel bottom, and wherein the channel bottom is coated with a firstinsulating metal oxide barrier layer as a result of the firstanodization step; a protective treatment, wherein the protectivetreatment induces hydrophobic surfaces to the channel walls and channelbottoms; a second anodization step after the protective treatment,wherein the second anodization step substantially removes the firstinsulating metal oxide barrier layer from the channel bottoms, inducesanodization only at the bottoms of the plurality of channels, andcreates a second insulating metal oxide barrier layer at the channelbottoms; and an etching step in an etching solution, wherein the etchingstep removes the second insulating metal oxide barrier layer from thechannel bottoms.
 2. The method according to claim 1, wherein the valvemetal layer comprises a layer of aluminum, an aluminum alloy, titanium,a titanium alloy, tantalum, or a tantalum alloy.
 3. The method accordingto claim 1, wherein the protective treatment comprises annealing at atemperature between 300° C. and 550° C.
 4. The method according to claim1, wherein the protective treatment comprises depositing a protectivelayer on the channel walls and on the channel bottoms, and wherein thesecond anodization step further removes the protective layer only fromthe channel bottoms.
 5. The method according to claim 4, wherein theprotective layer comprises hydrophobic silane or a polymer that isresistant to the etching solution.
 6. The method according to claim 4,wherein the protective layer comprises a polymer, and wherein thepolymer comprises polystyrene, poly(methy 2-methylpropanoate), orpoly(dimethylsiloxane).
 7. The method according to claim 1, wherein theetching solution is an aqueous etching solution comprising phosphoricacid, sulfuric acid, oxalic acid, chromic acid, ammonia, hydrogenperoxide, or potassium hydroxide.
 8. The method according to claim 1,wherein the etching solution comprises a surface tension adjustingagent.
 9. The method according to claim 1, further comprising providingultrasonic waves during the second anodization step.
 10. The methodaccording to claim 1, wherein the first anodization step anodizes only apart of the valve metal layer in the thickness direction to form thetemplate and a substrate supporting the template, and wherein thesubstrate comprises a remaining, non-anodized part of the valve metallayer.
 11. A template comprising a plurality of spaced channels alignedlongitudinally along a first direction, wherein the template is obtainedby a method for transforming at least part of a valve metal layer intothe template, the method comprising: a first anodization step comprisinganodizing at least part of the valve metal layer in a thicknessdirection to form a porous layer of valve metal oxide comprising aplurality of channels, wherein each channel has channel walls alignedlongitudinally along the first direction and has a channel bottom, andwherein the channel bottom is coated with a first insulating metal oxidebarrier layer as a result of the first anodization step; a protectivetreatment, wherein the protective treatment induces hydrophobic surfacesto the channel walls and channel bottoms; a second anodization stepafter the protective treatment, wherein the second anodization stepsubstantially removes the first insulating metal oxide barrier layerfrom the channel bottoms, induces anodization only at the bottoms of theplurality of channels, and creates a second insulating metal oxidebarrier layer at the channel bottoms; and an etching step in an etchingsolution, wherein the etching step removes the second insulating metaloxide barrier layer from the channel bottoms.
 12. The template accordingto claim 11, wherein the first direction is at an angle between 60° and90° with respect to a surface of the valve metal layer.
 13. The templateaccording to claim 11, wherein the template further comprises aplurality of interconnecting channels oriented along a second directiondifferent from the first direction.
 14. The template according to claim13, wherein the second direction is substantially orthogonal to thefirst direction.
 15. The template according to claim 11, wherein theplurality of spaced channels aligned longitudinally along the firstdirection have a diameter that is substantially constant along theirentire length, and wherein the channel bottoms expose an electricallyconductive layer.
 16. The template according to claim 11, wherein theplurality of spaced channels aligned longitudinally along the firstdirection have a diameter that is smaller than a spacing betweenneighboring channels.
 17. A method for forming a plurality of spacedstructures on a substrate, the method comprising: transforming at leastpart of a valve metal layer into a template comprising a plurality ofspaced channels aligned longitudinally along a first direction to formthe template and the substrate, wherein transforming at least part ofthe valve metal layer into the template comprises: a first anodizationstep comprising anodizing at least part of the valve metal layer in athickness direction to form a porous layer of valve metal oxidecomprising a plurality of channels, wherein each channel has channelwalls aligned longitudinally along the first direction and has a channelbottom, and wherein the channel bottom is coated with a first insulatingmetal oxide barrier layer as a result of the first anodization step; aprotective treatment, wherein the protective treatment induceshydrophobic surfaces to the channel walls and channel bottoms; a secondanodization step after the protective treatment, wherein the secondanodization step substantially removes the first insulating metal oxidebarrier layer from the channel bottoms, induces anodization only at thebottoms of the plurality of channels, and creates a second insulatingmetal oxide barrier layer at the channel bottoms; and an etching step inan etching solution, wherein the etching step removes the secondinsulating metal oxide barrier layer from the channel bottoms; anddepositing a solid functional material within the channels of thetemplate to form the plurality of spaced structures inside the pluralityof spaced channels, wherein the plurality of spaced structures arealigned longitudinally along the first direction.
 18. The method forforming a plurality of spaced structures according to claim 17, whereindepositing the solid functional material comprises depositing anelectrically conductive material, a semiconductor material, or anelectrically insulating material.
 19. The method for forming a pluralityof spaced structures according to claim 17, wherein depositing the solidfunctional material comprises depositing an electrically conductivematerial by galvanostatic electrodeposition, potentiostaticelectrodeposition, or plating to form a plurality of spaced electricallyconductive structures.
 20. The method for forming a plurality of spacedstructures according to claim 19, wherein the substrate is anelectrically conductive substrate and wherein an electrical contact isestablished between the plurality of spaced electrically conductivestructures and the substrate, and wherein the electrical contact has acontact resistance lower than 1 Ohm cm².
 21. (canceled)
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 26. (canceled) 27.(canceled)
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